WO2009079730A2 - Prisme et laser compact à cavité annulaire plane, à monofréquence unidirectionnel sans éléments intra-cavité - Google Patents

Prisme et laser compact à cavité annulaire plane, à monofréquence unidirectionnel sans éléments intra-cavité Download PDF

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Publication number
WO2009079730A2
WO2009079730A2 PCT/BR2008/000397 BR2008000397W WO2009079730A2 WO 2009079730 A2 WO2009079730 A2 WO 2009079730A2 BR 2008000397 W BR2008000397 W BR 2008000397W WO 2009079730 A2 WO2009079730 A2 WO 2009079730A2
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laser
ring cavity
planar ring
prism
oscillation according
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WO2009079730A3 (fr
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Flávio CALDAS DA CRUZ
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State University of Campinas
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08059—Constructional details of the reflector, e.g. shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08004—Construction or shape of optical resonators or components thereof incorporating a dispersive element, e.g. a prism for wavelength selection
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08018—Mode suppression
    • H01S3/08022—Longitudinal modes
    • H01S3/08027—Longitudinal modes by a filter, e.g. a Fabry-Perot filter is used for wavelength setting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08054—Passive cavity elements acting on the polarization, e.g. a polarizer for branching or walk-off compensation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/0813—Configuration of resonator
    • H01S3/0816—Configuration of resonator having 4 reflectors, e.g. Z-shaped resonators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/083—Ring lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/1062—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using a controlled passive interferometer, e.g. a Fabry-Perot etalon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/139—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/162—Solid materials characterised by an active (lasing) ion transition metal
    • H01S3/1623—Solid materials characterised by an active (lasing) ion transition metal chromium, e.g. Alexandrite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/1631—Solid materials characterised by a crystal matrix aluminate
    • H01S3/1633—BeAl2O4, i.e. Chrysoberyl
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/1645—Solid materials characterised by a crystal matrix halide
    • H01S3/1648—Solid materials characterised by a crystal matrix halide with the formula XYZF6 (Colquiriite structure), wherein X is Li, Na, K or Rb, Y is Mg, Ca, Sr, Cd or Ba and Z is Al, Sc or Ga

Definitions

  • This invention relates generally to the field of ring cavity lasers, and particularly it relates to solid-state, single-frequency and tunable lasers, such as those based on Ti-sapphire, GnLISAF, Alexandrite, Nd:YAG, or Nd:YVO 4 crystals.
  • Lasers are generally constructed with planar optical cavities in linear or ring configurations. It is well known that in the case of continuous-wave (cw) lasers, ring cavities offer the advantage to achieve single-frequency operation with higher power because it avoids the effect of spatial hole-burning in the gain medium (A. E. Siegman, Lasers, univ. Sci. Books, Sausalito, CA, 1986). For linear cavities, the nodes of stationary-waves created by counterpropagating beams leave regions of available gain which can be used by other modes of the laser cavity. Even when frequency selective elements are used, such as birrefringent filters, etalons, etc, linear cavities may not provide single- frequency operation.
  • Ring cavities avoid this problem, since the counterpropagating beams are traveling waves which do not cause spatial hole-burning.
  • laser oscillation in ring cavities occurs in both possible directions and is almost always desirable that unidirectional oscillation is established.
  • Oscillation in a single direction of a ring cavity usually requires the use of an intracavity element such as an optical diode (CE. Wagstaff and M. H. Dunn, J. Phys. D, 12 (1979) 355-368).
  • the most common type employs the discrimination provided by the Faraday effect, which causes a polarization rotation which depends on the propagation direction. This rotation is typically compensated by rotation by optical activity in another element such as a thin quartz plate, or by a half waveplate. The result is higher loss for one direction, since the rotated polarization implies in higher reflection losses at other surfaces in the laser cavity.
  • These devices however add complexity to the laser design and introduce optical insertion loss which reduces the laser output power.
  • unidirectional laser oscillation in planar ring cavities can be achieved through the use one or more intracavity optical components.
  • Such intracavity devices are unappealing because they add complexity to the laser design and also add losses to the laser cavity that reduce the laser output power.
  • Another object of the present invention is to provide a special prism used both as the laser output coupler and as an optical component which enforce unidirectional oscillation. Because no intracavity elements are used to achieve unidirectional oscillation, it is thus possible to achieve higher useful output power, lower cost and very small physical size.
  • this output-coupler-prism has a partially reflecting coating in one of its face that is part of the laser cavity.
  • This coating reflectivity is such that maximizes the output power, as a regular output coupler mirror.
  • the prism angles are such that one of those beams (called the first beam) is totally transmitted by the second face at Brewster's angle, and constitutes the laser output beam.
  • the other beam (called the second beam) is totally reflected at this same face by total internal reflection.
  • This second beam then insides in the third remaining prism face, which has a high reflecting coating, and is retroreflected along its optical path. This beam is therefore reinjected into the laser cavity, and is responsible to eliminating the laser oscillation in that direction. Laser oscillation then occurs only in the direction of the first beam.
  • this output-coupler-prism also has a partially reflecting coating in its face that is part of the laser cavity.
  • the second face has a coating such that strongly transmits one of the beams, that insides at a given incidence angle, and strongly reflects the other beam that insides at another incidence angle.
  • This second beam then insides the third prism face, that has a high reflecting coating, at normal incidence (zero degree) and is retroreflected along the same direction.
  • This beam is then reinjected into the laser cavity, and is responsible for eliminating the laser oscillation in that direction. Laser oscillation then occurs only in the direction of the first beam.
  • a further object of the present invention is to provide a compact ring laser whose cavity is constructed with materials of low thermal expansion coefficient, such as fused silica, INVAR, carbon fiber, Zerodur and ULE.
  • a further object of the present invention is to provide a compact ring laser whose cavity has a monolithic design in order to provide high mechanical stability, with reduced sensitivity to acoustic and vibrational noise.
  • a further object of the present invention is to provide a compact ring laser which combines a small physical size with the use of low thermal expansion materials, to achieve cavity length fluctuations, induced by vibrational and thermal noise, smaller than or on the order of the wavelength. For visible or near infrared lasers, this can be a few hundred nanometers.
  • Another object of the present invention is to provide a compact planar ring cavity laser system which, in addition to achieving unidirectional oscillation as described above, also oscillates in a single longitudinal mode (single- frequency). This is accomplished by constructing the laser cavity with small physical size using low thermal expansion materials. With these two features, the cavity passive length fluctuations, induced by thermal and vibrational (acoustic, seismic) noise, are on the order of or smaller than the laser wavelength. In this way, phase stability is preserved for the retroreflected beam from the output-coupler-prism, and no active servo-control for this retroreflected light is necessary. This phase stability ensures stable single-frequency operation. If necessary, an active control of the temperature of the laser cavity can be employed to assure long-term single-frequency oscillation.
  • a further object of the present invention is to provide a compact ring laser which uses frequency selective elements inside the cavity, such as a birefringent filter, one or two etalons or a Bragg grating, in order to achieve single-frequency oscillation in lasers with large gain bandwidth such as Ti:sapphire, Cr:LISAF, Alexandrite, and others.
  • frequency selective elements inside the cavity such as a birefringent filter, one or two etalons or a Bragg grating
  • a further object of the present invention is to provide a planar ring cavity laser system which, because of its small size, allows for tight focus in the gain medium, and therefore allows for very low threshold.
  • demonstrated prototypes of Ti:sapphire lasers achieve threshold of 300 mW when pumped by a single-frequency laser at 532nm. This low threshold makes possible to use pump lasers with 1 or 2 Watts of output power to pump a Tr.sapphire laser. Output powers of 1.5 W have been demonstrated for a Ti:sapphire laser pumped by 5 Watts at 532 nm.
  • Yet a further object of the present invention is to provide a planar ring cavity laser system which is unidirectional, single-frequency and has no intracavity elements, except the gain media, such as a Ti: sapphire crystal.
  • the gain media such as a Ti: sapphire crystal.
  • a reflective volume Bragg grating is used both as a cavity mirror and as a frequency selective element. This design greatly simplifies the versions of single-frequency tunable lasers (such as Ti: sapphire) available today and should imply into a significant reduction in costs and size.
  • a further object of the present invention is to provide a planar ring cavity laser system which is unidirectional and operate in mode-locked regime, producing ultra-short pulses.
  • Mode-locking is either active or passive, in this last case through the mechanism of Kerr lensing.
  • chirped mirrors are used for the laser cavity in order to produce negative group velocity dispersion, which compensates the positive group velocity dispersion introduced by the gain medium.
  • a prism pair can be used instead of chirped mirrors, to introduce negative group velocity dispersion.
  • the use of the output-coupler- prism assures unidirectional oscillation of the ring cavity always in the desired direction and, therefore without need of any other component for this purpose.
  • FIG.l is an illustration of a prior art ring cavity laser using an optical diode based on Faraday rotation to achieve unidirectional oscillation.
  • a Faraday crystal (28), such as TGG, is placed at Brewster angle under a magnetic field produced by permanent magnets.
  • a thin quartz plate (30) or a waveplate compensates the Faraday rotation.
  • FIG.2 is an illustration of a prior art ring cavity laser configured for unidirectional and single-frequency oscillation.
  • the laser cavity includes an optical diode (30) (Fig.l), a birrefringent filter (32) and two etalons (34,36), one of which is thin (36) and the other thick (34), and this last one can be formed by two prisms such as its length can be varied.
  • FIG.3 is an illustration of another prior art ring cavity laser configured for unidirectional and single-frequency oscillation.
  • the cavity includes an optical diode (30), a birrefringent filter (32) and only one etalon (34) to achieve unidirectional and single-frequency oscillation.
  • FIG.4 is a schematic diagram of the special prism used as the output coupler of the compact ring cavity laser of the present invention.
  • FIG.5 is a schematic diagram illustrating one embodiment of the compact ring cavity laser of the present invention with a reflecting volume Bragg grating (24) used as one of the cavity mirrors and also as a frequency selective element to achieve single-frequency oscillation.
  • a prism (28) is used both as the output coupler and to enforce unidirectional oscillation.
  • FIG.6 is a schematic diagram illustrating one embodiment of the compact ring cavity laser of the present invention with a transmission volume Bragg grating (30) is used as a frequency selective element to achieve single-frequency oscillation.
  • a prism (28) is used both as the output coupler and to enforce unidirectional oscillation.
  • FIG.7 is a schematic diagram illustrating one embodiment of the compact ring cavity laser of the present invention in which a birrefringent filter (30) and a thin etalon (32) are used as frequency selective elements to achieve single- frequency oscillation.
  • a prism (28) of figure 4 is used both as the output coupler and to enforce unidirectional oscillation.
  • FIG.8 is a schematic diagram illustrating one embodiment of the compact ring cavity laser of the present invention in which two etalons (30,32) are used as frequency selective elements to achieve single-frequency oscillation.
  • a prism (28) is used both as the output coupler and to enforce unidirectional oscillation.
  • FIG.9 is a schematic diagram illustrating one embodiment of the compact ring cavity laser of the present invention in which chirped mirrors (18, 22, 24) are used to achieve mode-locking.
  • a prism (28) is used both as output coupler and to enforce stable unidirectional oscillation.
  • a prism 18 is used as the laser output coupler and at the same time as an optical element that enforces unidirectional oscillation. It has internal angles ⁇ (12), ⁇ (14) and ⁇ (16) and faces 6, 8 and 10.
  • the two counterpropagating beams 2 and 4 circulating inside the ring cavity and having linear polarizations in the plane of FIG.4, inside at face 6 of the prism 18, with angles ⁇ .
  • Face 6 has a partially transmitting coating with reflectivity optimized for maximum laser output power, as a regular output coupler mirror. Beams 2 and 4 refract at the prism with angles ⁇ , as shown in figure 4.
  • Beam 2 inside on face 8 of the prism at Brewster angle ⁇ B tg " ⁇ (l/ ⁇ ), where n is the index of refraction of the prism material at the laser wavelength ⁇ . Beam 2 is then totally transmitted and constitutes the useful output beam. Beam 4, instead, suffers total internal reflection at face 8 and insides at face 10 at normal incidence (zero degree). Face 10 has a high reflecting coating, so that beam 4 is totally reflected and is then redirected towards the cavity along the same path.
  • the face 8 of the prism has a coating such that beam 2 is highly transmitted and beam 4 is highly reflected at their different incidence angles.
  • the prism does not need to be constructed with the angles mentioned above, however the coating of face 8 is more difficult to be done, since for a small angle variation it should go from highly reflector to highly transmissive.
  • a pump laser 10 is directed by mirrors 12 along the path 14 towards the laser cavity.
  • a pump lens 16 is used to focus the pump beam into the gain medium 20, and to match the parameters of the pump beam to the ones of the laser cavity.
  • the laser cavity is formed by mirrors 18 and 22, by a reflective Bragg grating 24 also used as a mirror, and by the output-coupler-prism 28, described in Fig. 4.
  • the reflective Bragg grating works both as a cavity mirror and as a frequency selective element. Its use in a ring cavity ensures single-frequency oscillation even for large gain bandwidth lasers such as Ti:sapphire, CnLISAF or Alexandrite.
  • the grating 24 is chirped, in which case it can be translated transversely for wavelength selection and tuning. In another embodiment, if the grating 24 has fixed period (e.g, is not chirped), it is rotated in order to do tuning.
  • the rotation of grating 24 is done by a galvanometer or a servo motor.
  • control of the grating angle is done digitally by a computer, microcontroller, microprocessor or digital signal processor (DSP).
  • the laser wavelength is calibrated externally by a spectrum analyzer or spectrometer, so that the grating angular position is mapped into laser wavelength.
  • a microcontroller, microprocessor or computer stores these values such that, after calibration, tuning to a desired wavelength is done digitally in a simple way.
  • a largely tunable laser such as Ti:sapphire or CnLISAF, is then wavelength calibrated once at the factory, which eliminates the need for a laser wavelength meter by the user, except when recalibration becomes necessary. Fine tuning of the laser wavelength is done by a piezo element 26 that supports one of the cavity mirrors 18 or 22, or even the Bragg grating 24.
  • a pump laser 10 is directed by mirrors 12 along the path 14 towards the laser cavity.
  • a pump lens 16 is used to focus the pump beam into the gain medium 20, and to match the parameters of the pump beam to the ones of the laser cavity.
  • the ring cavity is formed by mirrors 18, 22, 24, by a transmission Bragg grating 30 and by the output-coupler-prism 28, described in Fig. 4.
  • the transmission Bragg grating works as a frequency selective element. Its use in a ring cavity ensures single-frequency oscillation even for large gain bandwidth lasers such as Tksapphire, CnLISAF or Alexandrite.
  • the grating 24 can be chirped, in which case it can be translated transversely for wavelength selection and tuning. Alternately, if its period is fixed (e.g., is not chirped), it can be rotated for perform wavelength tuning.
  • the mirror 24 (or another mirror of the laser cavity) is supported by the piezo 26, which is used either for fine wavelength tuning or as an actuator for laser frequency control.
  • a pump laser 10 is directed by mirrors 12 along the path 14 towards the laser cavity.
  • a pump lens 16 is used to focus the pump beam into the gain medium 20, and to match the pump beam parameters to the ones of the laser cavity.
  • the ring cavity is formed by mirrors 18, 22, 24, a birefringent filter 30, a thin etalon 32 and by the output-coupler-prism 28, described in Fig. 4.
  • the birefringent filter 30 and the thin etalon 32 work together as frequency selective elements to enforce single- frequency oscillation. Their use in a ring cavity ensures single- frequency oscillation even for large gain bandwidth lasers such as Ti:sapphire, CnLISAF or Alexandrite.
  • the birefringent filter 30 and etalon 32 are precisely rotated by a galvanometer or a servo motor.
  • control of the etalon angle is done digitally by a computer, microcontroller, microprocessor or digital signal processor (DSP).
  • the laser wavelength is calibrated externally by a spectrum analyzer or spectrometer, so that the etalon angular position is mapped into laser wavelength.
  • a microcontroller, microprocessor or computer stores these values such that, after calibration, tuning to a desired wavelength is done digitally in a simple way.
  • a largely tunable laser such as Ti:sap ⁇ hire or CnLISAF, is then wavelength calibrated once at the factory, which eliminates the need for a laser wavelength meter by the user, except when recalibration becomes necessary.
  • the mirror 24 (or another mirror of the laser cavity) is supported by the piezo element 26, which is used for fine wavelength tuning or as an actuator for laser frequency control.
  • a pump laser 10 is directed by mirrors 12 along the path 14 towards the laser cavity.
  • a pump lens 16 is used to focus the pump beam into the gain medium 20, and to match the pump beam parameters to the ones of the laser cavity.
  • the ring cavity is formed by mirrors 18, 22, 24, by two thin etalons 30 and 32 and by the output-coupler-prism 28, described in Fig. 4.
  • the thin etalons 30 and 32 work together as frequency selective elements and can have slightly different thickness, so that their transmission peaks coincide at very large spectral intervals (in a Vernier effect), which can be several TeraHertz.
  • the etalons 30 and 32 are precisely rotated by a galvanometer or a servo-motor. In this last case, simultaneous control of both etalon angles is done digitally by a computer, microcontroller, microprocessor or digital signal processor (DSP).
  • the laser wavelength is calibrated externally by a spectrum analyzer or spectrometer, so that the etalons angular positions are mapped into laser wavelength.
  • a microcontroller, microprocessor or computer stores these values such that, after calibration, tuning to a desired wavelength is done digitally in a simple way.
  • a proper algorithm that maps the angular position of both etalons into wavelength is used by the microprocessor.
  • a largely tunable laser such as Ti:sapphire or CnLISAF, is then wavelength calibrated once at the factory, which eliminates the need for a laser wavelength meter by the user, except when recalibration becomes necessary.
  • the mirror 24 (or another mirror of the laser cavity) is supported by the piezo 26, which is used for fine wavelength tuning or as an actuator for laser frequency control.
  • a pump laser 10 is directed by mirrors 12 along the path 14 towards the laser cavity.
  • a pump lens 16 is used to focus the pump beam into the gain medium 20, and to match the pump beam parameters to the ones of the laser cavity.
  • the ring cavity is formed by mirrors 18, 22, 24, and by the output-coupler prism 28, described in Fig. 4. Either one of the mirrors 18, 22, and 24, or even the coating of the output-coupler prism , can be dispersive (chirped) such as to introduce negative group velocity dispersion, such as to compensate the positive dispersion introduced by the gain medium.
  • the output-coupler-prism assures unidirectional oscillation of the ring cavity mode-locked laser and eliminates, therefore, any intracavity element used for this purpose, such as for example, acousto-optical modulators used today for this purpose in various commercial models.
  • the mirror 24 (or another mirror of the laser cavity) is positioned by the piezoelectric transducer 26, which can be used as actuator to stabilize the repetition rate of the mode-locked laser.
  • a prism pair instead of chirped mirrors, is used inside the laser cavity to introduce negative group velocity dispersion. This is a usual method employed today to produce ultrashort pulses through the mechanism of passive Kerr lens mode-locking.

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  • Physics & Mathematics (AREA)
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  • Lasers (AREA)

Abstract

L'invention concerne un laser compact à cavité annulaire plane qui produit une oscillation laser unidirectionnelle sans recours à des éléments intra-cavité, et qui fonctionne selon un régime monofréquence. Un prisme spécial est utilisé comme coupleur de sortie; les propriétés de réflexion interne de ce prisme s'utilisent pour sélectionner l'une des deux directions d'oscillation possibles de la cavité annulaire. Le dessin compact et l'absence d'éléments intra-cavité permettent d'obtenir des puissances de sortie plus élevées. Un fonctionnement stable monofréquence peut être obtenu grâce à l'utilisation combinée d'éléments sélecteurs de fréquence tels que des réseaux de Bragg épais, d'étalons ou des filtres biréfringents, alliés à la compacité du dessin de la cavité, laquelle peut inclure une structure monolithique, ainsi qu'à l'utilisation de matériaux de structure à a faible coefficient de dilatation thermique.
PCT/BR2008/000397 2007-12-20 2008-12-19 Prisme et laser compact à cavité annulaire plane, à monofréquence unidirectionnel sans éléments intra-cavité Ceased WO2009079730A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
BRPI0705854A BRPI0705854B1 (pt) 2007-12-20 2007-12-20 prisma, e laser compacto unidirecional, de frequência-única, com cavidade de geometria plana em anel sem elementos intracavidade
BRPI0705854-3 2007-12-20

Publications (2)

Publication Number Publication Date
WO2009079730A2 true WO2009079730A2 (fr) 2009-07-02
WO2009079730A3 WO2009079730A3 (fr) 2009-12-10

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PCT/BR2008/000397 Ceased WO2009079730A2 (fr) 2007-12-20 2008-12-19 Prisme et laser compact à cavité annulaire plane, à monofréquence unidirectionnel sans éléments intra-cavité

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BR (1) BRPI0705854B1 (fr)
WO (1) WO2009079730A2 (fr)

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JP2020504333A (ja) * 2017-01-06 2020-02-06 マッコーリー ユニバーシティー シングル縦モードリングラマンレーザ
WO2021191593A3 (fr) * 2020-03-23 2021-11-04 Fraunhofer Uk Research Ltd Appareil laser mono-fréquence
WO2023080242A1 (fr) * 2021-11-08 2023-05-11 大学共同利用機関法人自然科学研究機構 Élément optique, dispositif optique et procédé de production d'élément optique
WO2025037107A3 (fr) * 2023-08-14 2025-03-27 Skylark Lasers Ltd Laser

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6868106B1 (en) * 1998-06-04 2005-03-15 Lambda Physik Ag Resonator optics for high power UV lasers

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020504333A (ja) * 2017-01-06 2020-02-06 マッコーリー ユニバーシティー シングル縦モードリングラマンレーザ
US11322905B2 (en) 2017-01-06 2022-05-03 Macquarie University Single longitudinal mode ring Raman laser
JP7175274B2 (ja) 2017-01-06 2022-11-18 マッコーリー ユニバーシティー シングル縦モードリングラマンレーザ
WO2021191593A3 (fr) * 2020-03-23 2021-11-04 Fraunhofer Uk Research Ltd Appareil laser mono-fréquence
WO2023080242A1 (fr) * 2021-11-08 2023-05-11 大学共同利用機関法人自然科学研究機構 Élément optique, dispositif optique et procédé de production d'élément optique
JP2023069750A (ja) * 2021-11-08 2023-05-18 大学共同利用機関法人自然科学研究機構 光学素子、光学装置および光学素子の製造方法
WO2025037107A3 (fr) * 2023-08-14 2025-03-27 Skylark Lasers Ltd Laser

Also Published As

Publication number Publication date
BRPI0705854A2 (pt) 2009-08-18
WO2009079730A3 (fr) 2009-12-10
BRPI0705854B1 (pt) 2018-10-16

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