JPH03112183A - Light beam/scanning device - Google Patents

Abstract

PURPOSE:To achieve light beam scanning by providing a current injection/non- injection regions and a light-emitting element, an element drive circuit, and a grating where an activation layer is in quantum well structure. CONSTITUTION:An n-Al GaAs 11, an activation layer 12 in quantum well structure, a p-AlGaAs 13, and a P<+>-GaAs 14 are superposed on an n-GaAs substrate 10. Both sides are eliminated by etching up to the middle of the depth of a layer 13 and are buried by a heat resistant polyimide resin 15. Electrodes 19 and 18 in a specified structure are provided. A part without the electrode 18 is a current non-injection region (Lab). This ridge type end face light-emitting element produces a larger light output as the pulse width of the drive current is longer if the drive current is the same, and this tendency is stronger as the dimension Lab is longer. Also, the light-emitting center wavelength is greatly shifted in the vicinity of laser oscillation when the drive time or current is changed. The output of a light-emitting element 20 is allowed to enter into a diffraction grid 22 and is deflected according to the wavelength utilizing this phenomenon, thus enabling a beam to be scanned (jump or shift of light position).

Description

[Detailed description of the invention] Background of the invention The present invention relates to a light beam scanning device.

Conventional devices for scanning light beams are mainly those using polygon mirrors as typified by laser beam printers. However, the beam scanning method using a polygon mirror has the problem of slow response speed and low nine-position repeatability because it has a movable part.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light beam scanning device having no mechanically moving parts.

The optical beam scanning device according to the present invention is a semiconductor light emitting device which has a current injection region and a current non-injection region, an active layer has a quantum well structure, and one emission center wavelength is dependent on driving current or driving time. , a drive circuit capable of controlling the drive current level or drive time of the semiconductor light emitting device;
and a grating that deflects the emission beam of the semiconductor light emitting element according to the emission wavelength thereof.

This invention utilizes the phenomenon in which the emission center wavelength of the semiconductor light emitting device changes significantly near the critical point of laser oscillation by changing the drive current level or drive current pulse width, and by combining this with a grating, the light beam can be adjusted. Achieved scanning. This eliminates the need for any mechanically movable parts, making it possible to scan the light beam using only electrical control.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is used in this invention. This figure shows the structure of a ridge waveguide type semiconductor edge emitting device that has a current injection region and a current non-injection region, and whose active layer has a quantum well structure.

In this figure, on an n-GaAs substrate IO, an n-
AJ GaAs cladding layer 11. ORIORlN-8
CH-(Graded Index-9eparate
Confinement Heterostrut
ure-MultiQuantum Well) Active layer 12. P-AjGaAs cladding layer 13 and p''
-GaAs cap layers 14 are sequentially stacked. p-
AI GaAs cladding layer 13 and p-GaAs
The cap layer 14 has p-Aj GaAs cladding layers 18 on both sides so as to form an elongated ridge in the center.
A buried layer 15 made of heat-resistant polyimide resin having electrical insulation properties is provided in the portion removed by this etching. The lower surface of this semiconductor light emitting device has an AuGeN1 alloy/
An n-side electrode 19 with a double structure made of Au is provided on the upper surface, and a p-side electrode 18 with a double structure made of Cr/Au is provided only on a part of the upper surface. The p-side electrode 18 is provided on the light emitting end surface side, the part where the p-side electrode 18 is provided is a current injection region, and the part where the p-side electrode 18 is not provided is a non-excitation absorption region (m-injection region). ). active layer 12
An example of the nearby He1 composition and the film thickness of each layer is shown in FIG.

When a driving (excitation) current is passed between the side electrodes 18 and 19.

Since there are resin buried layers 15 on both sides of the ridge, the current flows concentratedly in the ridge part, which is also the ridge part of the current injection region.
Light emission (non-laser light emission and laser light emission) having the characteristics described below is generated.

The active layer may have a quantum well structure, and may be a single quantum well. As the buried layer material, a high-resistance semiconductor material (for example, amorphous Si) may be used in addition to polyimide resin. Furthermore, p-type and n-type may be reversed. Further A
j Semiconductor materials other than GaAs can also be used.

It has been found that such a ridge waveguide type semiconductor edge emitting device has the following characteristics.

(1) The drive current 7 starting output characteristics have drive current pulse width dependence.

FIGS. 3A to 3C show the output characteristics of seven driving currents when the semiconductor light emitting device described above is driven with a square wave current. 2, 3, 5, 1 mouth, 2Q#see indicates the pulse width (parameter) of the square wave drive current.

CW represents continuous drive. Figure 3 (A) shows the case where the length L ah of the non-excited absorption region is 600 ja+.
B) When the beam and noodles are 4001 trr, the same figure (C) shows the length of the current injection region when Ib is 200μ rin. Both are 200jm.

These graphs show that as the drive current pulse width increases, the laser oscillation threshold current and the oscillation threshold optical output decrease, and this tendency becomes more pronounced as the length L ah of the non-excited absorption region increases. That is, when a drive current of the same value is applied, the longer the pulse width of the drive current, the greater the optical output can be obtained.

(2) The emission center wavelength has large drive time dependence and drive current dependence.

FIGS. 4(A) to 4(C) show the time waveforms of the drive current pulse and the light emission output pulse. L, -2001m,
L,,m 600gm, drive current 1=125II^
Figure 4 (A) shows the pulse width of the driving current is 21 seconds, Figure 4 (B) shows the pulse width of 31 seconds, Figure 4 (C
) is of 5 μs'e c. Pulse width is 31se
Above c.

For a constant value of drive current, the optical output pulse exhibits a time response in which it decreases at first and then rises in the middle. The longer the pulse width, the greater the rise of the optical output pulse.

FIGS. 5(A) to 5(D) also show the time waveforms of the drive current pulse and the light emission output pulse, where Lo =
200jo+, L,, m 6QOgm, and the pulse width of the drive current was kept constant at 2jscc. Fig. 5(A) shows the driving current of 1-1ooolA, and Fig. 5(B) shows the driving current of I m 120.
aA, same figure (C) is 1-130IIA r same figure (D)
is the case of I-140aA. From this figure, it can be seen that as the drive current increases, the rise of the optical output shifts to the left and becomes steeper.

Figure 6 shows a model of the waveform of the optical output pulse, where point A is the initial point of optical output, point B is the point when the optical output decreases, and point C is the point when the optical output rises. shall be.

FIG. 7 shows the emission spectra of the points A, B, and C. At points A and B, the wavelength λ is 75
While it shows a peak near 0■, at point C, the emission center wavelength shifts to the long wavelength side by about 20 nm, resulting in 770
A peak is shown near t++g.

There is no laser emission at points A and B, and laser oscillation occurs at point C. In this way, it can be seen that even with a constant drive current, the emission center wavelength shifts (jumps) significantly depending on the drive duration (pulse width).

Figure 8 shows the drive current/light output characteristics shown in Figure 3,
Points E, F and G are taken on this characteristic curve.

Figure 9 shows the emission spectra at these points E, F, and G.

Points D, E, and F have a peak around a wavelength of about 750 nm, but at point G, where laser oscillation is occurring, the emission center wavelength is similarly shifted to around 770 rv.

As described above, the semiconductor light emitting device described above has the characteristic that the emission center wavelength shifts significantly depending on the drive time and drive current.

In the light beam scanning device according to the present invention, the semiconductor light emitting element shown in FIG. is large (20n
The beam spot is switched positionally by utilizing the phenomenon of shifting (about 100 m), and an example of its configuration is shown in the first
This is shown in Figure O.

The light emission output of the semiconductor light emitting device 20 described above is collimated by a lens 21 and enters a grating (diffraction grating) 22 . The grating 22 deflects the incident light according to its wavelength (there are reflection types and transmission types).
be. The drive circuit 23 of the semiconductor light emitting device 20 is capable of changing the pulse width of the drive current or the drive current value.

When the pulse width of the drive current applied from the drive circuit 23 to the semiconductor light emitting device 20 is approximately from point A to point B shown in FIG. 6, the emission center wavelength of the semiconductor light emitting device 20 is 75
0na+, and the light beam spot generated by the grating 22 is at the position indicated by PAR. If the pulse width of the drive current is made longer from point A to point C shown in Figure 6, one light emitting element 20 will oscillate as a laser, and the center wavelength will be about 770n11, so the beam spot will be PAC. Move to the position shown. Scanning the light beam (jumping or shifting the position of the light beam spot) by changing the pulse width of the drive current in this way
can be done.

As explained with reference to Figures 8 and 9, the emission center wavelength can be changed by keeping the pulse width constant and changing the drive current value, so scanning of the light beam can be achieved in the same way. can.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a ridge waveguide type semiconductor edge-emitting device in which the active layer has a quantum well structure and a II flow non-injection region, and FIG. 2 is a graph showing the A1 composition near the active layer. Figures 3 (A) to (C) are graphs showing the drive current/light output characteristics of the same semiconductor edge emitting device, and Figures 4 (^) to (
C) and FIGS. 5(A) to (D) are waveform diagrams showing the drive current pulse and light emission output pulse of the same element, FIG. 6 is a modeled representation of the optical output pulse of the same element, and FIG. The figure is a graph showing the emission spectrum at point A-C shown in Fig. 6, Fig. 8 is a graph showing the driving current/light output characteristics of the same element, and Fig. 9 is the emission spectrum at point D-G shown in Fig. 8. It is a graph showing a spectrum. FIG. 1O shows an embodiment of the present invention and is a diagram showing the configuration of a light beam scanning device. 20...Semiconductor light emitting device. 22... Grating. 23... Drive circuit. that's all

Claims (1)

[Scope of Claims] A semiconductor light emitting device having a current injection region and a current non-injection region, an active layer having a quantum well structure, and a light emission center wavelength dependent on driving current or driving time; A light beam scanning device comprising: a drive circuit capable of controlling the drive current level or drive time of the element; and a grating that deflects the emission beam of the semiconductor light emitting element according to its emission wavelength.