CN108683070A - A kind of ultrafast laser generator - Google Patents

Abstract

The invention discloses an ultrafast laser generator and relates to the technical field of lasers. It includes: a saturable absorber, a laser crystal, an electro-optic modulator, a polarizing mirror and a high-reflecting mirror arranged in sequence on a preset axis, the polarizing mirror and the axis have a preset angle, and the electro-optic modulator is used to When the output laser meets the preset conditions, the polarization direction of the laser is changed, so that the laser is reflected and output from the polarizing mirror, and an ultrafast laser is obtained. The ultrafast laser generator provided by the invention can stably generate ultrafast laser with short pulse width and high energy, and has the advantages of simple structure and small volume.

Description

An Ultrafast Laser Generator

technical field

The invention relates to the field of laser technology, in particular to an ultrafast laser generator.

Background technique

Due to its short pulse time and high peak power, ultrafast lasers are widely used in scientific research and production activities. Existing ultrafast lasers are usually generated by SESAM (Semiconductor Saturable Absorber Mirror) mode-locked cavity-stabilized oscillators, ultrafast pulse chirped amplifiers, and disc-medium mode-locked oscillators.

Existing ultrafast laser generators have the following problems: complex structure, large volume, and unable to stably generate ultrafast laser pulse output with short pulse width and large single pulse energy.

Contents of the invention

The technical problem to be solved by the present invention is to provide an ultrafast laser generator for the deficiencies of the prior art.

The technical scheme that the present invention solves the problems of the technologies described above is as follows:

An ultrafast laser generator, comprising: a saturable absorber, a laser crystal, an electro-optic modulator, a polarizing mirror and a high-reflecting mirror arranged in sequence on a preset axis, the polarizing mirror and the axis have a preset The angle is set, and the electro-optic modulator is used to change the polarization direction of the laser light when the laser light output from the high reflection mirror satisfies a preset condition, so that the laser light is reflected and output from the polarization reflector to obtain ultrafast laser light .

The beneficial effects of the present invention are: the ultrafast laser generator provided by the present invention can stably generate ultrafast laser with short pulse width and high energy, and has the advantages of simple structure and small volume.

Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

Fig. 1 is the structural representation that the embodiment of a kind of ultrafast laser generator of the present invention provides;

Fig. 2 is a structural schematic diagram provided by another embodiment of an ultrafast laser generator of the present invention.

Detailed ways

The principles and features of the present invention will be described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

As shown in Figure 1, it is a structural schematic diagram provided for an embodiment of an ultrafast laser generator of the present invention. The dotted line in the figure represents the laser light path, and the ultrafast laser generator includes: saturable absorbers arranged in sequence on a preset axis 1. Laser crystal 2, electro-optic modulator 3, polarizing mirror 4 and high-reflecting mirror 5, the angle between polarizing mirror 4 and the axis is preset, and the electro-optic modulator 3 is used when the laser output from high-reflecting mirror 5 satisfies Under preset conditions, the polarization direction of the laser light is changed so that the laser light is reflected and output from the polarizing mirror 4 to obtain an ultrafast laser light.

It should be noted that the preset axis may be the direction in which the laser oscillates between the saturable absorber 1 and the high reflection mirror 5 .

It should be understood that in order to generate laser light, the saturable absorber 1 should be kept parallel to the high reflective mirror 5, so that the laser reciprocates between the saturable absorber 1 and the high reflective mirror 5, and the initial light generated by the saturable absorber 1 should pass through the laser Crystal 2, which produces highly coherent polarized light.

It should be understood that in order to generate ultrafast laser light, the reflectivity of the high reflection mirror 5 may be 99.99%.

It should be understood that in order to produce ultrafast laser light, when the laser light reciprocates between the saturable absorber 1 and the high reflective mirror 5, most of the laser light should be able to transmit through the polarizing reflector 4, that is to say, the polarizing reflector 4 oscillates The reflectivity of the laser in the process should be as small as possible, and for the laser after changing the polarization direction, the reflectivity should be as large as possible, that is, the ratio of the reflectivity of the polarizing mirror 4 to the laser light before and after changing the polarization direction should be as close as possible 0: ∞.

For example, assuming that the polarization angle of the laser is a during the oscillation process, and the polarization angle of the laser is b after changing the polarization direction, then the reflectivity of the polarization mirror 4 to the laser with the polarization angle a should be close to 0; the polarization mirror 4 For the laser with polarization angle b, its reflectivity should be close to ∞.

It should be noted that, in order to enable the generated ultrafast laser to be output from between the saturable absorber 1 and the high reflector 5, the angle between the polarizing reflector 4 and the axis should be at a preset angle so that the ultrafast laser can be emitted. The angle can be set according to actual needs.

For example, in order to make the output of the ultrafast laser parallel to the preset axis, an angle of 45° can be formed between the polarizing mirror 4 and the axis.

It should be noted that, in order to generate ultrafast laser light, the ultrafast laser light can be output after the ultrafast laser light with short pulse width and high energy is produced, that is to say, the laser output from the high reflector 5 should meet the preset conditions The single pulse energy of the laser output from the high reflection mirror 5 can reach a preset energy value, and the preset energy value can be set according to actual needs.

The preset condition can also be other conditions, for example, the heat generated by the laser in a unit time, etc., can be used as the preset condition.

It should be noted that the electro-optic modulator 3 may include a Pockels cell, the Pockels cell may be placed on the laser oscillation route, the laser may pass through the Pockels cell during oscillation, and the Pockels cell may be subjected to high voltage. Change the refractive index of the electro-optic crystal in the Pockels cell to make it function as a half-wave plate, thereby changing the polarization direction of the laser.

It should be understood that the total loss from the saturable absorber 1 to the high reflection mirror 5 must be smaller than the gain generated by the laser crystal 2 after being pumped by the pumping light.

The ultrafast laser generator provided in this embodiment can stably generate ultrafast laser with short pulse width and high energy, and has the advantages of simple structure and small volume.

Some optional embodiments of the present invention will be described below in conjunction with FIG. 2 . The dotted lines in the figure represent laser light paths, and the solid lines represent wired or wireless connection modes.

Optionally, in some embodiments, the electro-optic modulator 3 may include: a Pockels cell 31 and a high-voltage signal generator 32, wherein the Pockels cells 31 are arranged on the axis and arranged between the laser crystal 2 and the polarizing mirror Between 4, the high-voltage signal generator 32 is used to send the high-voltage signal to the Pockels cell 31, and the Pockels cell 31 is used to change the refractive index of the electro-optic crystal in the box according to the high-voltage signal, so that the laser light passing through the Pockels cell 31 The direction of polarization changes.

It should be understood that, in the initial state, the high voltage on the Pockels cell 31 can be set to 0, and when the pulse energy of the laser output from the high reflection mirror 5 reaches a preset value, it will be generated by the high voltage signal generator 32. High voltage changes the refractive index of the electro-optic crystal in the Pockels cell 31 to make it function as a half-wave plate.

Optionally, in some embodiments, the electro-optic modulator 3 may also include: a controller 33 and a photodetector 34, the photodetector 34 is arranged on the axis, and is used to detect the pulse energy of the laser output from the high reflection mirror 5 , the controller 33 is used to obtain pulse energy, and when the pulse energy reaches a preset value, drive the high voltage signal generator 32 to generate a high voltage signal.

It should be understood that when the pulse energy of the laser output from the high reflection mirror 5 reaches a preset value, the controller 33 can drive the high voltage signal generator 32 to generate a high voltage signal, but when the pulse energy of the laser output from the high reflection mirror 5 reaches When the value is less than the preset value, the controller 33 may stop driving the high-voltage signal generator 32 to generate a high-voltage signal. Its switching time is directly determined by the time of rising and falling edges of the high voltage loaded on the electro-optic crystal.

Optionally, in some embodiments, the photodetector 34 can also be used to detect the pulse time of the laser output from the high reflection mirror 5, and the controller 33 is also used to, according to the pulse time and the cavity length of the ultrafast laser generator, The time when the high-voltage signal generator 32 is driven to generate the high-voltage signal is obtained, and the high-voltage signal generator 32 is driven to generate the high-voltage signal at the time.

Optionally, in some embodiments, a vibration isolation platform may also be included.

Optionally, in some embodiments, a cooling device may also be included, and the cooling device is arranged in the heat sink of the laser crystal 2 .

It should be understood that the laser crystal 2 needs to be actively cooled, and the cooling device may be a water-cooled pipeline, which is arranged in the heat sink of the laser crystal 2 for cooling the laser crystal 2 .

Since the function of the multi-pass reflective cavity in the laser generator is to prolong the length of the laser cavity, the resonant cavity in this application is equivalent to only consisting of three parts: a saturable absorber 1, a laser crystal 2, and a high reflection mirror 5. When the pumping laser is input into the laser crystal 2 from the saturable absorber 1, the lower energy level particles of the laser crystal 2 are pumped to the upper energy level, forming a population inversion and outputting ultrafast laser pulses from the high reflection mirror 5. At this time, the single pulse energy of the output laser pulse can be obtained by detecting the photodetector 34 . When the ultrafast laser generator reaches a dynamic balance, the photodetector 34 can detect a stable ultrafast laser pulse output.

Since the reflectivity of the high reflection mirror 5 is very high, the laser single pulse energy oscillating in the resonant cavity at this time is far greater than the single pulse energy output from the high reflection mirror 5 . Taking the reflectivity of 99.99% as an example, the single pulse energy of the intracavity laser is 10,000 times that of the laser single pulse output from the high reflection mirror 5 . When the single pulse energy monitored by the controller 33 reaches the set expected value, the refractive index of the electro-optic crystal in the Pockels cell 31 is changed by controlling the high-voltage signal input into the Pockels cell 31, so that it realizes the half-wave plate effect, Therefore, the laser pulse oscillating in the cavity is completely output from the polarizing mirror 4 . This means that the single pulse energy of the ultrafast pulse output at this time is several orders of magnitude higher than the pulse energy output from the high reflector 5, while the pulse width remains unchanged.

The output cavity mirrors of existing ultrafast laser seeds all have fixed reflectivity. In the design of the reflectivity of the output mirror, if the designed reflectivity is too low, the pulse width of the generated ultrafast pulse will be too large; if the designed reflectivity is too high, the output energy will be too low. Therefore, it is difficult to obtain high energy and short pulse width laser output directly through the ultrafast laser resonator. In the above-mentioned embodiments, the contradiction between short pulse width output and large energy output is solved by using the intracavity polarization coupling output method, and after proper intracavity parameter design, a single pulse ultrafast over 50 microjoules can be obtained. The laser output is at least 2 orders of magnitude higher than the single pulse output energy of the existing solid-state ultrafast laser oscillator.

Readers should understand that in the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the embodiments or examples are combined A particular feature, structure, material, or characteristic is described as included in at least one embodiment or example of the invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Those skilled in the art can clearly understand that for the convenience and brevity of the description, the specific working process of the above-described devices and units can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or modifications within the technical scope disclosed in the present invention. Replacement, these modifications or replacements shall all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (4)

1. a kind of ultrafast laser generator, it is characterized in that, comprises: saturable absorber, laser crystal, electro-optic modulator, polarizing reflector and high reflection mirror arranged successively on preset axis, described polarizing reflector and all There is a preset angle between the axes, and the electro-optic modulator is used to change the polarization direction of the laser light when the laser output from the high reflection mirror satisfies a preset condition, so that the laser light is reflected from the polarizing mirror Output, get ultrafast laser. 2. The ultrafast laser generator according to claim 1, wherein the electro-optic modulator comprises: a Pockels cell and a high-voltage signal generator, wherein the Pockels cells are arranged on the axis , arranged between the laser crystal and the polarizing mirror, the high-voltage signal generator is used to send a high-voltage signal to the Pockels cell, and the Pockels cell is used to change the The refractive index of the electro-optic crystal changes the polarization direction of the laser light passing through the Pockels cell. 3. The ultrafast laser generator according to claim 2, wherein the electro-optic modulator further comprises: a controller and a photodetector, and the photodetector is arranged on the axis for detecting from The pulse energy of the laser output by the high reflection mirror, the controller is used to obtain the pulse energy, and when the pulse energy reaches a preset value, drive the high-voltage signal generator to generate a high-voltage signal. 4. ultrafast laser generator according to claim 3, is characterized in that, described photodetector is also used for detecting the pulse time of the laser output from described high reflection mirror, and described controller is also used for according to described The pulse time and the cavity length of the ultrafast laser generator are used to obtain the moment when the high-voltage signal generator is driven to generate a high-voltage signal, and the high-voltage signal generator is driven to generate a high-voltage signal at the moment.