JPH02296387A - Array laser - Google Patents

Abstract

PURPOSE:To prevent the generation of the shift of a focal point due to a difference in wavelength between the time of record and the time of reproduction for confirmation by a method wherein the light emitting position of a laser device for record use and the light emitting position of a laser device for confirmation reproduction use are shifted in their emitting directions. CONSTITUTION:In order to perform reproduction for confirmation while recording is being made, a laser device 20a for record use is driven by pulse current according to a signal while inclines to record and a laser device 20b for confirmation reproduction use is driven by a DC current. There is a difference in wavelength between lights which are emitted from the devices 20a and 20b. In this case, as the light emitting position of a beam for confirmation reproduction use of a long wavelength is located at a position more part to an optical system than that of a beam for record use to the optical system, the focal positions the lights in after they pass through the optical system result in making uniform even if the optical system has a color aberration. Thereby, the generation of the shift of a focal point due to a difference in wavelength between the time of record and the time of reproduction for confirmation can be prevented.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an array laser.

[Conventional technology]

FIG. 2 is a perspective view of a conventional array laser chip, which is an example of a conventional array laser chip having two light emitting sections. In the figure, p-〇aA
An n -GaAs IJi block layer (2) is grown on the s substrate (1) by, for example, a liquid phase growth method, and after removing part of the block layer (2) in two stripes, the p -A
nGaAs lower cladding layer (3), A-gGaAs S active 7# (4), rl-AfflGaAs upper cladding layer (5)
Then, an n-GaAs contact layer (6) is grown in this order. Striped (the distance between the removed parts is, for example, 1.00 μm, 8 degrees). Contact layer (
6) Form the upper electrode (7) and the electrode (8) on the substrate side,
The two light emitting parts are separated by a separation groove (9) that reaches the substrate. The wafer crystal produced as described above is cleaved in a direction perpendicular to the stripes to form a resonator end face u0. When a negative voltage is applied to the electrode (8), the current is narrowed down to a stripe shape in the blocking layer (2), and the active layer (4) above the groove is efficiently injected. While the light emitted from the active layer (4) travels back and forth between the cavity end faces (this is amplified), it is transmitted from the cavity end face to the outside of the chip (
This is emitted. The n-side of the Nzatinop is electrically isolated by a separation groove (9), and the distance between the two light emitting parts is 10
Since they are separated by 0 μm and 8 degrees, the two elements can emit light independently without interference. The emission positions of the two beams are within the same cleavage plane.

FIG. 3 is an explanatory diagram showing the main parts of a conventional two-beam write-once optical disk device using the above array laser. The laser light emitted from the array laser aυ passes through a collimation lens and becomes parallel light. , Prism 03. beam splinter α
After passing through the 1/4 wavelength plate α, the light is focused by the objective lens a, and is irradiated northward onto the optical disk in the form of a spot with a diameter of about 1 μm.

For recording, the element (lla) of the array laser 0υ shown in FIG. 2 is driven in pulses according to the signal to be recorded.

For example, an optical pulse with a peak optical output of 313 mW is emitted from the array laser element (na). If the transmittance of the optical system (from the collimator lens 02 to the objective lens (171) is 30, for example, the diameter of 1 μm on the disk Q81 is
A light of 9rnW is irradiated to a range of about The recording surface of the original disk decoy (this is coated with a Te-based alloy thin film, for example. This alloy thin film θ) absorbs light at the point where the Brosbot comes out, rapidly generates heat, and the alloy thin film evaporates. do.

Light pulse (corresponding to this)
Signals can be recorded.

The recorded information is read out using an array laser element (n
This is carried out using the emitted light of b). Array laser element (
Ilb) is driven by DC and outputs a light output of, for example, 3 mW. Light C passes through the same optical system as during recording, and passes through the top of the disk (
This is illuminated with light of fl and 9 mw. The light is reflected by the recording surface of the disk, and the reflected light is sent to the objective lens (1?), 1
The light enters the light receiving element QljF via the /4 wavelength plate α, the beam splinter 0, and the lens α0. Optical disc 08)
The light reflectance is different between parts with and without bits. Therefore, the amount of reflected light incident on the light receiving element changes depending on the presence or absence of bits. Information can be read by detecting the presence or absence of hints from this light ti conversion.

In this conventional embodiment, a recording laser element (lla
) and a reproduction laser element (TLB) are provided separately, so one signal can be recorded and reproduced continuously.In other words, there is no need to wait for the disk to rotate to see if the recording is accurate or not. It is possible to confirm the details (real time record @ error detection).

FIG. 4 shows a wavelength versus optical output characteristic curve diagram of this array laser. The recording beam is operated at, for example, 30 mW as described above. The confirmation reproduction beam is operated at, for example, 3 mW.

At this time, the wavelengths of the two beams are longer, for example, by about 5 nm, with the confirmation reproduction beam being longer.

Normally, an optical system has chromatic aberration, and this chromatic aberration causes the focal positions of the recording light spot and the confirmation/reproduction light bulb to shift. The deviation of the image point due to the objective lens is, for example, 5n
A wavelength variation of m corresponds to about 0.75 μm. This defocus (therefore, only some - 10,000 beams are in focus, degrading the recording or reproducing characteristics).

[Problem to be solved by the invention]

Conventional array lasers were configured as described above, with a recording beam and a confirmation/reproduction beam.

Since the two beams are arranged in the same plane with respect to the emission direction, there is a problem in that the wavelength difference between the two beams causes chromatic aberration of the optical system and causes defocusing.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to obtain an array laser for an optical disk in which no focal shift occurs due to a wavelength difference between recording and confirmation reproduction.

[Means to solve the problem]

In the annoy V-za according to the present invention, the light emitting position of the recording laser element (resonator end face) and the light emitting position of the confirming and reproducing V-the element are shifted in the emission direction.

[Function] In this invention, the deviation in the emission direction between the light emission position of the recording V-enment and the light emission position of the confirmation and reproduction laser element is caused by the optical system (thereby causing a recording beam and a confirmation and reproduction beam. cancel out the focal position difference between

〔Example〕

Hereinafter, one embodiment of the present invention will be explained in detail.In FIG. The difference from the conventional one is that the emission position of the confirmation and reproduction laser beam (resonator end face) is lower than the emission position of the recording laser beam in the emission direction.

To achieve this, the end face of the resonator for confirmation reproduction may be etched using, for example, an FIB (focused ion beam). Like the cleavage plane, the etching plane acts as a co-grasp mirror. The depth from the end surface should be such that the focal shift on the disk surface caused by the wavelength difference between the two beams and the focal shift due to the shift in the light emission positions of the two beams cancel each other out. .

In this embodiment, in order to perform confirmation playback while recording, the recording sensor element (20a) is pulse-driven (for example, with an optical output of 311 m
W) L/, DC drive (for example, optical output 3rnW) the confirming reproduction element (20b). The light ζ emitted from the recording element (20a) and the confirmation/reproduction device (20b) is, for example, 5 nm, similar to the conventional one.
There is a wavelength difference of However, since the light exit position of the confirmation and reproduction beam with a long wavelength is located further away from the optical system than the recording beam, even if the optical system has chromatic aberration, the light that passes through the optical system is The subsequent focal positions will be aligned.

Although the above embodiment has been explained using a write-once optical disc as an example, the same effect as described above can be obtained in the case of a rewritable optical disc.

In addition, in the above embodiment, the case where the oscillation wavelength of the confirmation and reproduction beam is longer is explained, but when the oscillation wavelength of the recording beam is longer (in this case, conversely, the oscillation wavelength of the recording element is etched and the emission position is All you have to do is lower it.

Moreover, in the above embodiment, A/? In the case of GaAs-based materials (Have I explained this carefully? AIK; materials other than aAs-based materials, such as InGaAs P-based, AlgaInP
The same effect as above can be obtained in systems.

Furthermore, in the above embodiment, an internal stripe type using a p-substrate is used as the V-the structure, but the same effect as above can be obtained even if it is an n-substrate or other 7-a structure. There is.

In the above embodiment, FIB was used as an example of the etching method, but other methods such as chemical etching can also have the same effect as above, as long as the etched surface becomes a mirror surface.

Furthermore, although the above example shows the case where only the vicinity of the light emitting part of the element is etched, the same effect as above can be obtained even if part of the element, including the substrate, is etched entirely. be.

〔Effect of the invention〕

As described above, according to the present invention, the output position of the recording beam of the monolink file laser and the output position of the confirmation/reproduction beam are configured so that they rub in the output direction (rubbing), so that the optical system does not need to be changed in any way. , there is an effect that an anoy laser without focal position deviation can be obtained at low cost and with good M degree.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of an irradiator according to an embodiment of the present invention, FIG. 2 is a perspective view showing the structure of a conventional array laser chip, and FIG. 3 is a main part of a conventional two-beam write-once optical disk device. The configuration explanatory diagram, FIG. 4, shows a wavelength-optical output characteristic curve diagram of a conventional A V inser. In the figure, (1) is the substrate, and (2) is the current block layer. (3) is the lower cladding layer, (4) is the active layer, (5) is the upper cladding layer, (6) is the contact layer, (7) 18) is the electrode, (9) C is the isolation groove, and Q is the resonance Vessel end surface, (211a)
is the laser element for recording, (Δlb) is the V for confirmation playback
- indicates the element. In addition, in the figure, the same reference numerals are the same, and 0 indicates the part corresponding to O'i.

Claims (1)

[Claims] In a monolithic array laser that has two or more light emitting parts in the same chip and emits two or more laser beams, the emission position of at least one laser beam is shifted with respect to the beam emission direction. Characteristic array laser.