JP2009302365A - Driving method of semiconductor laser device and semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a following problem: in a conventional semiconductor laser device and a driving method thereof, it is difficult to reduce both the magnitude of a spontaneously emitted light of non-oscillating time of the laser and the magnitude of oscillation delay time of oscillating time, particularly in a semiconductor laser device in which the length of a resonator is lengthened in order to emit a high optical output power. <P>SOLUTION: The driving method of the semiconductor laser device and the semiconductor laser device includes: a semiconductor laser 4 having an electrode 5 in which a current can be injected into a part of region of an active layer and an electrode 6 in which the current can be injected into the remaining other active regions; a laser driving circuit 2 to supply the current to the electrode 5; a laser driving circuit 3 to supply the current to the electrode 6; and a control circuit 1 to control the laser driving circuit 2, 3. When emitting an optical output power, the current injection to the electrode 5 is made to precede to the current injection to the electrode 6, when zeroing the optical output power, the current to the electrode 5 is reduced to be an equivalent threshold current or less, the current of the electrode 6 is reduced to be less than the equivalent threshold current. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser element driving method using a semiconductor and a laser apparatus, and more particularly to a semiconductor laser element driving method and a semiconductor laser apparatus used as a signal light source for display display.

  In recent years, flat panel displays using liquid crystal or plasma have become the mainstream instead of cathode ray tubes as display devices for televisions and personal computers (PCs). Furthermore, new display methods such as organic EL have been proposed and developed. Among them, a laser display that scans a thin beam and displays an image on a screen is newly attracting attention. The laser display uses a micro electro mechanical systems (MEMS) mirror that can be downsized to reflect the beam light to the MEMS mirror, while the MEMS mirror is periodically tilted up, down, left, and right to scan the beam light and display the image. It is reflected on the screen.

  As the light source, laser light having excellent monochromaticity and capable of condensing the beam in a small area is used. Such a laser display is characterized by excellent color reproducibility due to the use of laser light and focus-free properties that do not require focusing. The latter, in particular, has a unique feature that other displays cannot project on an oblique screen or curved wall. Such laser display technology is disclosed in, for example, Patent Document 1 and Patent Document 2.

  On the other hand, semiconductor lasers having multiple electrodes are disclosed in, for example, Patent Document 3 and Patent Document 4. Patent Document 3 discloses a semiconductor laser having a saturable absorber at the center of the semiconductor laser and an electrode on each semiconductor upper surface in the optical axis direction in order to realize an optical inverter. An optical inverter is realized by utilizing the nonlinear characteristic of the optical output current characteristic of the saturable absorber.

  In Patent Document 4, a bistable semiconductor laser is disclosed. An active layer including a light amplification region and a saturable absorption region is provided, and an independent electrode is provided for each region.

JP 2008-9074 A JP 2008-15390 A JP-A 61-65224 JP 2007-134490 A

  In the prior art disclosed in Patent Document 1 and Patent Document 2, as laser display devices, red, green, and blue laser lights are modulated on the basis of image data and then combined on one optical axis, and the light is combined into a MEMS mirror. Is used to scan and project an image on the screen. FIG. 11 shows a schematic diagram of an example of such a laser display device. In FIG. 11, 101R is a red laser, 101B is a blue laser, 101G is a green laser, and 102 is a lens that condenses the laser light and shapes it into a parallel light beam. Reference numerals 103 and 104 denote dichroic mirrors that reflect only a specific wavelength band and transmit the others, and focus light beams of three colors on one axis through this mirror. Reference numeral 105 denotes a MEMS mirror that can be tilted in two axial directions, and scans an image using the resonance phenomenon of the MEMS. A screen 106 displays an image.

  As the laser light source, red and blue semiconductor lasers are used. Green does not currently have a practical semiconductor laser, so there is a solid-state pump laser that converts 1060 nm laser light to 530 nm green, which is half the wavelength, using second harmonic generation (SHG). in use. However, since the development of green semiconductor lasers is also active, it is expected that green semiconductor lasers will be put into practical use. When the semiconductor laser is a light source, it is easy to change the gradation of brightness by modulating the light intensity of the semiconductor laser or the pulse width of the light emission time within a certain time. Changing the light intensity is called light intensity modulation, and changing the light emission time is called pulse width modulation.

  As an example, FIG. 12 shows a state of light modulation when the brightness gradations of four adjacent pixels during scanning increase in order. (A) is a semiconductor laser light intensity modulation method, and (B) is a pulse width modulation method. Initially, the light intensity increases in the order where the gradation is lowest, that is, the light output is zero. In (A), the pixel changes continuously between pixels, but the light intensity may be reduced to zero once between pixels. In the pulse width modulation method, gradation is created using an afterimage of the human eye. In any case, the place where the gradation is lowest is a state where no laser oscillation occurs.

That is, the light output of the semiconductor laser shown in FIG. 13 - In current characteristics, typically, the semiconductor laser of the threshold current I _th in the bias given therefrom gradation, for example, when light of P ₁ are required I _1. When light of P ₂ is necessary, I ₂ is injected into the semiconductor laser. However, in this case, light is emitted from the semiconductor laser by spontaneous emission light in the semiconductor laser even when an I _th current that originally has zero light is injected. Although this light depends on the laser structure, it is usually about 0.2 mW to 0.8 mW and cannot be ignored. Therefore, the contrast deteriorates from the viewpoint of display performance. Since a recent flat panel display has a contrast of 10 ⁴ or more, the laser display also needs a contrast of 10 ⁴ or more in order to produce a high-definition image. However, as described above, with this driving method, the contrast is limited to about 100 due to spontaneous emission from the semiconductor laser.

In order to increase the contrast, it is conceivable to make the current completely zero instead of biasing to I _th when it is desired to set the lowest gradation, that is, zero light. However, in this case, since there is an oscillation delay time peculiar to the semiconductor laser, the next signal of 0 oscillates with a delay, so that the image is not as data and is destroyed.

The oscillation delay time is a phenomenon in which the semiconductor laser oscillates behind the injection current when a current higher than the threshold current is injected when biased below the threshold current as shown in FIG. This is a phenomenon that occurs because the lifetime of carriers (electrons and holes) in the semiconductor laser is extremely slow compared to the lifetime of light. For this reason, there is a pattern effect in which the oscillation delay time varies depending on the pattern of the input current, and the oscillation delay time becomes longer if the time of 0 when there is no light output is long. The oscillation delay time τ _d when a rectangular wave current having a sufficient interval compared to the carrier lifetime when the bias current is 0 is input to the semiconductor laser can be expressed by the following equation (1).

ここでτ_nはキャリア寿命時間、I_mは駆動電流、I_bはバイアス電流、I_thはしきい電流であり、バイアス電流は自然放出光を低減するためにしきい電流以下、望ましくは０とする。

Here, τ _n is a carrier lifetime, _Im is a drive current, I _b is a bias current, and I _th is a threshold current. The bias current is equal to or less than a threshold current, preferably 0, in order to reduce spontaneous emission light. .

  When the light gradation is performed by pulse width control, since the dark gradation has a narrow pulse width, the time when there is no light output is long, so the oscillation delay time becomes long, and the light output does not reach the specified output.

  Although the display time per pixel in the display depends on the method, it is about 90 ns for NTSC and about 6 ns for high-definition systems, which is very fast. On the other hand, as a typical example of a semiconductor laser, when the carrier lifetime is 2 ns, the threshold current is 40 mA, the drive current is 50 mA, and the bias current is 0 mA to increase the contrast, the maximum oscillation delay time is 3. 2 ns. This value is a value that cannot be ignored even with the NTSC system of the conventional display system, and it can be said that drawing is difficult in the high-vision system. Furthermore, this oscillation delay time is a case where laser oscillation is performed with a sufficient interval compared to the carrier lifetime, and becomes shorter depending on the number of carriers existing in the semiconductor laser, that is, it is large in the signal of the previous pixel. Therefore, the magnitude of the oscillation delay time can be uneven in the light intensity of the pixel.

In the above equation (1), the oscillation delay time changes when the drive current changes. For example, in the above example, when the driving current is doubled to 100 mA, the oscillation delay time is reduced to about 1 ns. However, as can be seen from FIG. 13, the drive current has to be set to a predetermined value in order to determine the light intensity. In FIG. 13, the drive current refers to a current component after laser oscillation at, for example, I ₁ -I _th or I ₂ -I _th . Therefore, there is a very large limitation on increasing the drive current in order to reduce the oscillation delay time. In addition, since the light intensity necessary for drawing depends on the color sensitivity perceived by a person, the drive current differs depending on each color of the laser. Further, since the materials of the semiconductor lasers of the respective colors are different, the laser characteristics such as the threshold current and the carrier lifetime are different. Therefore, the oscillation delay time differs greatly for each color, which causes color unevenness in the initial display of pixels.

  Thus, a high contrast and a reduction in oscillation delay time are a trade-off, which hinders high performance of the laser display. This trade-off is particularly noticeable when trying to increase the resonator length in order to increase the optical output of the semiconductor laser. This is because the threshold current increases as the resonator length increases, and the oscillation delay time increases as the threshold current increases as can be seen from the above equation (1). Therefore, it is difficult to improve the above trade-off in a laser display that requires high light output.

  On the other hand, with the techniques disclosed in Patent Document 3 and Patent Document 4, the trade-off cannot be solved by increasing the contrast and reducing the oscillation delay time, which are the problems of the present invention. Further, in general, when there is a saturable absorber in the resonator structure, there is a problem that the semiconductor portion of the saturable absorber portion is damaged and reliability cannot be obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser driving method and a semiconductor laser device in which both an oscillation delay time and spontaneous emission light are small and a high optical output can be obtained.

  Still another object of the present invention is to provide a semiconductor laser driving method and a semiconductor laser device in which unevenness of light intensity and unevenness of color are suppressed.

  A representative example of the present invention is as follows. That is, the present invention is a method of driving a semiconductor laser provided with a control circuit, wherein the semiconductor laser is provided with a resonator structure, and light is provided in the resonator structure and is resonated by the resonator structure. An optical waveguide structure; an active layer provided in the optical waveguide structure; a first electrode for injecting current into a partial region of the active layer; and a second for injecting current into another region of the active layer. And the main light output is emitted from the end face of the optical waveguide structure on the second electrode side, and the level of the light output of the semiconductor laser is injected into the first electrode. The timing of light emission of the light output is controlled by the value of current injected into the second electrode.

  With the driving method and the semiconductor laser device of the present invention, it is possible to realize a light source in which the spontaneous emission light from the main laser emission side is extremely small when the semiconductor laser is not oscillating and the oscillation delay time is small when the semiconductor laser oscillates. In particular, the effect is remarkable in a semiconductor laser having a long resonance length capable of obtaining a high optical output.

  A typical embodiment of the present invention is as follows. In other words, the laser driving method of the present invention provides a semiconductor laser having a first electrode capable of injecting current into a part of the active layer and a second electrode capable of injecting current into the remaining other active layer region. When outputting, the current injection to the first electrode side is preceded by the current injection of the second electrode. Further, when the light output is extinguished (the light output is set to 0), the current to the first electrode is reduced below the equivalent threshold current, and the current of the second electrode is reduced to the equivalent threshold current. Reduce to less than. During quenching, the current value injected into the first electrode and the current value injected into the second electrode are controlled at substantially the same timing. In the present invention, “light output is 0” means a state in which the light output of a signal in an image information processing circuit or the like is 0. In this state, the spontaneous emission from the semiconductor laser is very small but completely emitted. It goes without saying that is not always zero.

  The semiconductor laser device of the present invention includes a first laser driving circuit for driving the semiconductor laser connected to the semiconductor laser and the first electrode operated by the driving method, and a semiconductor connected to the second electrode. This is achieved by comprising a second laser driving circuit for driving the laser and a control circuit for controlling the first and second laser driving circuits.

  In another embodiment of the present invention, the active layer includes a first electrode capable of injecting current into a partial region of the active layer and a second electrode capable of injecting current into the remaining other active layer region. The semiconductor switch circuit in which the current flowing through the third electrode is connected to the third electrode in the semiconductor laser passing through the third electrode and drives the semiconductor laser, and one is connected to the second electrode and the other is connected to the power source The laser driving circuit and a control circuit for controlling the switch circuit are configured, and the first electrode is connected to a power source and is operated by the laser driving method.

With the driving method and the semiconductor laser device of the present invention, it is possible to realize a light source in which the spontaneous emission light from the main laser emission side is extremely small when the semiconductor laser is not oscillating and the oscillation delay time is small when the semiconductor laser oscillates. In particular, the effect is remarkable in a semiconductor laser having a long resonance length capable of obtaining a high optical output. Further, the manufacturing method of the semiconductor laser is almost the same as the conventional one, and the laser driving circuit, the semiconductor switch circuit, and the control circuit can be realized with the same specifications as the conventional one, and can be realized at low cost.
Embodiments of the present invention will be described below with reference to the drawings.

  A method of driving the semiconductor laser device according to the first embodiment of the present invention will be described with reference to FIGS. Here, an embodiment applied to driving a blue light source of a scanning laser display will be described. 1 to 3 show the configuration of the light source device. FIG. 1 is a schematic diagram showing an outline of the configuration of a semiconductor laser, and the semiconductor laser shows a longitudinal section. FIG. 2 is a perspective view of the semiconductor laser of FIG. An example of a more detailed cross-sectional structure from the light emission direction of FIG. 2 is shown in FIG.

  In FIG. 1, reference numeral 1 denotes a control circuit that controls the semiconductor laser drive circuits 2 and 3 based on image information. Reference numeral 4 denotes a semiconductor laser, which is a blue semiconductor laser grown on a GaN substrate having a p-side electrode divided into two. 5 and 6 are p-side electrodes, and 7 is an n-side electrode. The p-side electrode is divided into a first electrode 5 and a second electrode 6. The semiconductor laser drive circuit 2 drives the second electrode 6, and the semiconductor laser drive circuit 3 drives the first electrode 5. In this embodiment, the blue semiconductor laser is operated by the light intensity modulation method. Reference numeral 8 denotes an InGaN quantum well active layer of the semiconductor laser, and reference numerals 9 and 10 denote reflection coat films. The reflection coat film 10 reflects the reflection coat film 10 more than the reflection coat film 9 in order to output light from the reflection coat film 10 as a light source. The rate is getting smaller. A signal based on the image information is input to the control circuit 1 from the outside, but the input signal line is omitted here.

  2 and 3 are enlarged views of the semiconductor laser 4 portion. The semiconductor laser 4 includes a resonator structure in which the reflective coating films 9 and 10 are used as a reflecting mirror, an optical waveguide structure that is provided in the resonator structure and that resonates with the resonator structure, and in the waveguide. The active layer 8 (35) is provided between the first conductivity type semiconductor layer 41 and the second conductivity type layer 42. A first electrode 5 in contact with the first conductivity type semiconductor layer 41 and injecting a current into a partial region of the active layer 8 through a partial region of the first conductivity type semiconductor layer; A second electrode 6 in contact with the first conductivity type semiconductor layer 41 and injecting current into another region of the active layer 8 through another region of the first conductivity type semiconductor layer. . As shown by arrows in FIG. 2, the reflective coating film is designed so that main light is emitted from the end of the optical waveguide structure on the second electrode side. That is, the reflectance of the reflective coating film 10 on the side from which main light is emitted is low, and the reflectance of the reflective coating film 9 on the opposite side is increased. For example, the reflectance of the reflective coating film 10 is selected to be about 10%, and the reflectance of the reflective coating film 9 is selected to be about 90%.

  In FIG. 3, 31 is a GaN semiconductor substrate, 32 is an n-type AlGaN cladding layer, 33 is an n-type GaN guide layer, 34 is an InGaN guide layer, 35 is an active layer, 36 is an InGaN guide layer, 37 is an AlGaN electron stopper layer, Reference numeral 38 denotes a p-type AlGaN / GaN superlattice cladding layer, 39 denotes a p-type GaN contact layer, 40 denotes a dielectric film, 41 denotes a p-type electrode, and 42 denotes an n-type electrode.

In light emitting direction of FIG. 2 (arrow), the first electrode 5 current I ₁ is injected, the second electrode 6 are current I ₂ is injected. In the axial direction of the semiconductor laser 4, that is, in the light emission direction (arrow direction), the length of the active layer region (active layer region of the electrode 5) of the semiconductor laser 4 corresponding to the first electrode 5 is L1, the second The length of the active layer region corresponding to the electrode 6 (the active layer region of the electrode 6) is L2. When the width W of the active layer 8 of the semiconductor laser 4 is constant, the electrode 5 for the active layer total area S _t of the semiconductor laser, the area of the active layer current is injected from the electrode 6 S _{1 (=} L1 × The ratio of W) and S ₂ (= L1 × W), that is, S ₁ / S _t and S ₂ / S _t are adjusted according to the sizes of L 1 and L ₂ . Needless to say, when the width W of the active layer 8 changes, the rate of current injection is adjusted by the actual area of each of the regions S ₁ and S ₂ of the active layer instead of L1 and L2.

In FIG. 1 or FIG. 2, it is desirable that the distance between the electrodes 5 and 6 is close to the extent that there is no region that is not injected into the active layer when a current is passed through both electrodes. In other words, the lengths of the electrodes 5 and 6 are approximately equal to L1 and L2, respectively. For example, the distance between the electrodes 5 and 6 is 2 to 20 μm. On the other hand, if the electrodes 5 and 6 are too close to each other, a leakage current is generated between the electrodes 5 and 6, but a leakage current may be generated. If there is a problem in control, a part of the p-type semiconductor is formed by proton implantation or the like. May be made highly insulating. As will be described later, it is desirable from the viewpoint of high speed that the regions S ₁ and S ₂ of the active layer are somewhat smaller in the second electrode. That is, when the width W of the active layer 8 is constant, the value multiplied by the ratio S1 / St of the active layer region S1 into which current is injected from the electrode 5 with respect to the region St of the entire active layer of the semiconductor laser is 0.5. It is desirable to be larger (L1> L2).

Next, the operation of the first embodiment will be described. FIG. 4 shows an example of the light output and the current control method for the electrodes 5 and 6 in the case of the light intensity modulation method, where (A) is the clock, (B) is the light output, and (C) is the electrode. 5 shows current I ₁ injected into 5 and (D) current I ₂ injected into electrode 6. Although the optical outputs and current signals of (B) to (D) are controlled (t1 to t6) in synchronization with the clock of (A), there are some differences between the actual optical outputs and current signals due to the structure of the semiconductor laser. There may be a difference in timing. As shown in (B), an example is shown in which the light intensity is changed by “0120310”.

Here, the threshold current when oscillating the implanted semiconductor laser current by short-circuiting the electrodes 5 and 6 of the semiconductor laser and I _th, from the electrode 5 to the active layer total area S _t of the semiconductor laser I _th × S ₁ / S _t multiplied by the ratio S ₁ / S _t of the region S ₁ of the active layer into which current is injected is defined as I _th1, and similarly, the active layer into which current is injected from the electrode 6 I _th × S ₂ / S _t multiplied by the ratio S ₂ / S _t of the region S ₂ is defined as I _th2 . In addition, the clock serves as a time control reference for the light intensity change, and depends on the MEMS scanning speed in the scanning laser display.

In FIG. 4, when the light intensity is initially 0, I ₁ is set to a current I _b1 smaller than I _th1 as shown in (C), and I ₂ is set to 0 smaller than I _{th2 as} shown in (D). Since it is set, the semiconductor laser does not oscillate. Further, the spontaneous emission light from the active layer region of the electrode 5 is zero because the active layer region of the electrode 6 absorbs light. At time t ₁ , the light intensity (light output) is set to 1, but as shown in (C), I ₁ precedes t ₁ by a half clock (Δt) and is greater than the threshold current I _{th1 by} “1”. Set to the current at which the optical output is generated. At this time (half clock preceding), since I ₂ remains 0, the active layer region of the electrode 6 absorbs light in the entire semiconductor laser, so that the laser does not oscillate, and the light output is 0 as shown in (B). It is. Further in this case, the active layer region of the electrode 6 absorbs light, so that the spontaneous emission light toward the end face coat 10 is zero.

Then, the laser oscillates is set from 0 to I ₂ as shown in at t ₁ (D) to the light output exiting current I _th2 larger "1", as shown in (B) "1" Light output. At this time already, since the threshold current or more current flows to the electrode 5, the oscillation delay time of the light output at t ₁ is smaller than the semiconductor laser of the same conventional active layer area, the following equation is the maximum value (2)

従来の式(１)のI_b＝０と比較すれば分るように、本実施例によれば、等価的にしきい電流がS２/St小さくなり発振遅延時間が大幅に減少する。

As can be seen from comparison with I _b = 0 in the conventional equation (1), according to this embodiment, the threshold current is equivalently reduced by S2 / St and the oscillation delay time is significantly reduced.

FIG. 5 shows an example in which the maximum oscillation delay time is calculated with S ₂ / _St as the horizontal axis. For example, a carrier life time is the threshold current is 40mA at 2ns, S _{2 /} S _t is 0.5, the maximum oscillation delay time when the driving current is 50 mA (thin solid line) is about 1.0 ns, the oscillation delay The time can be reduced to about 1/3 of the conventional structure. That is, as can be seen from the curves in FIG. 5 when τ _n : 2 ns, I _th : 40 mA, and I _m : 50 mA, the oscillation delay time can be greatly reduced by the light source device of the present invention and its driving method. Can do. This is the maximum value of the oscillation delay time. Actually, the carrier is excited by the carrier remaining in the active layer region of the electrode 6 by the previous signal or the spontaneous emission light from the active layer region of the electrode 5. The oscillation delay time is smaller than that of the equation (2).

Also, from FIG. 5, the oscillation delay time is almost halved when I _m : 100 mA (broken line) with a different drive current compared to when 50 _m . As described above, since the drive current is limited to determine the optical output, the oscillation delay time cannot be adjusted using the drive current as a parameter. Therefore, as seen from FIG. 5, it is possible to adjust the oscillation delay time to adjust the S _{2 /} S _t. This is very effective when the driving current is large for semiconductor lasers of different colors. As described above, since the pixel display time per pixel is 6 ns in the high vision system, the maximum oscillation delay time needs to be 1/10 or less. Therefore, S ₂ / S _t is desirably less than 0.5, and therefore S ₁ / S _t is desirably greater than 0.5.

Since generally the semiconductor laser has a threshold current I _th increases the smaller the tau _n, in FIG. _{5 τ n: 2 ns, I} th: 40 mA, I m: a 100 mA (dashed line), tau _n: As can be seen from the S ₁ / S _t dependence of the oscillation delay time in the case of 1.5 ns, I _th : 60 mA, and I _m : 100 mA (thick solid line), the semiconductor lasers of the same material can be used as much as possible. The oscillation delay time characteristics do not change significantly.

Returning to FIG. 4, the light intensity is set to “2” at t ₂ as shown in FIG. 4B. In this case, since there is no oscillation delay time, both I ₁ and I ₂ are set to a predetermined value at t _2. What is necessary is just to raise to the electric current equivalent to the light output of 2 ".

Furthermore, in the case of the "0" the light output at t ₃ is the I ₁ and I _b1 is less than the threshold current at t ₃ as shown in (C), the I ₂ as shown in (D) 0 And Here, it is important that I ₁ is less than the threshold current at t ₃ . This is because, since the laser has already oscillated, the laser oscillation often does not stop due to the saturable absorption phenomenon even if only I ₂ is less than the threshold current. Further, to increase the optical output to “3” at t ₄ , as shown in (C), I ₁ is increased to a current corresponding to the optical output of “3” in advance by a half clock (Δt), and (D increase in t ₄ as shown in) until the current light output equivalent I ₂ a "3". In this way, similarly to the case of the previous t _1, (B), the light output from t ₃ to t ₄ when including the spontaneous emission light is 0, very small oscillation delay in t ₄ Light output can be obtained in time.

Then, it is sufficient to decrease the current corresponding to "1" to I _1, I ₂ at t ₅ since no oscillation delay time when reduced to "1" the light output at t _5. If the light output to zero at t _6, the a I ₁ at t ₅ in the same manner as t ₃ and I _b1 is less than the threshold current I ₂ is zero.

  With the above semiconductor laser driving method, a laser light source in which both the oscillation delay time and the spontaneous emission light emission from the end face are reduced can be realized.

In this embodiment, the preceding time is a half clock, but the width of the preceding time may be an arbitrary value, and is not particularly limited to a half clock. In addition, if the active layer region of the electrode 5 is wide, the light output is mainly governed by the magnitude of the current flowing in the active layer region of the electrode 5, so that the current value of I ₂ does not necessarily have a current corresponding to the light output. There is no need to flow, for example, a certain value may flow. Alternatively, an on / off current less than the threshold current may be supplied.

Furthermore, from equation (2), the smaller the S ₂ , the smaller the oscillation delay time. Therefore, it is effective to reduce the active layer region of the electrode 6. However, if this active layer region is made too small, the spontaneous emission light from the active layer region of the electrode 5 cannot be absorbed and light is transmitted by the supersaturated absorption phenomenon, so that there is a limit.

  From the viewpoint of cost, it is desirable not to provide a structure in which the band cap changes in the waveguide, such as EA-DFB. From the viewpoint of reliability, it is desirable that there is no supersaturated absorption region in which no current is always injected into the active layer.

Needless to say, the direction of the injected current differs depending on the conductivity type of the semiconductor with which the electrodes 5 and 6 are in contact. Furthermore, the direction of the injection current of the electrode 6 is such that, for example, a photocurrent flows in the active layer region of the electrode 6 when the current of I ₁ increases to a current corresponding to “1” from half a clock before t _1. In such a case, the electrode 6 is controlled so that a current in the direction opposite to the direction of the current 5, that is, a current that absorbs the photocurrent flows. As for the semiconductor laser, a Fabry-Perot laser having two reflecting coats as a resonator is used. Needless to say, a similar result can be obtained by using a distributed feedback laser, that is, a DFB laser.

  Needless to say, the control method of the light source device according to the present embodiment can be applied not only to the blue laser but also to the green laser and the red laser.

  FIG. 6 shows a laser display light source for a laser display device in which the light source device of Example 1 is applied to each of blue, green, and red lasers. In FIG. 6, 1R, 1B, and 1G are control circuits that control the semiconductor laser drive circuits 2R and 3R, 2B and 3B, and 2G and 3G, respectively. 101G, 101B, and 101R are semiconductor lasers, 102 is a lens, 103 and 104 are dichroic mirrors, 105 is a MEMS mirror, and 106 is a screen. Reference numeral 107 denotes an image information processing circuit, and reference numeral 108 denotes a MEMS driving circuit. The control circuits 1R, 1B, and 1G are semiconductor laser driving circuits 2R, 3R, 2B, and 3B based on the image information signals of the respective colors from the image information processing circuit 107 and the current control method for the electrodes 5 and 6 described in FIG. , 2G, 3G are controlled. The image information processing circuit 107 controls the control circuits 1R, 1B, and 1G and the MEMS drive circuit 108 in synchronization, and displays an image on the screen 106.

  According to the present embodiment, the laser characteristics, particularly the spontaneous emission light and the carrier life time below the threshold current and the threshold current are different for each color, and the oscillation delay time characteristic and the spontaneous emission light intensity below the threshold current are different. Even in this case, it is possible to obtain a light emission characteristic with a small oscillation delay time and no spontaneous emission. Therefore, a laser display device capable of obtaining an image with little color unevenness can be provided. Since this laser display device has a simple display mechanism and does not require focusing, it can be miniaturized and portable, and the screen may be a wall of a room.

  With the driving method and the semiconductor laser device of this embodiment, it is possible to realize a light source in which the spontaneous emission light from the main laser emission side is extremely small when the semiconductor laser is not oscillating and the oscillation delay time is small when the semiconductor laser oscillates. . In particular, the effect is remarkable in a semiconductor laser having a long resonance length capable of obtaining a high optical output. Further, the manufacturing method of the semiconductor laser is almost the same as the conventional one, and the laser driving circuit, the semiconductor switch circuit, and the control circuit can be realized with the same specifications as the conventional one, and can be realized at low cost.

  Next, a second embodiment of the present invention will be described with reference to FIG. Here, an embodiment applied to driving a red light source of a scanning laser display will be described. The configuration of the light source device is the configuration shown in FIG. However, as the semiconductor laser, a red semiconductor laser having a wavelength of 635 nm using InGaAlP on a GaAs substrate as an active layer is used. The structure of the electrode division of the semiconductor laser is the same as that of the first embodiment. In this embodiment, the red semiconductor laser is operated by the pulse width modulation driving method.

  FIG. 7 shows the light output and the current control to the electrodes 5 and 6 in the case of the pulse width modulation driving method, and shows an example in which the light intensity is changed by “0120310”. In the case of the pulse width modulation system, one clock of FIG. 7 corresponding to one pixel is further divided into gradations for display. That is, it goes without saying that the frequency of the transmitter is divided into the number of color gradations, for example, 1024.

First, when the light intensity is 0, I ₁ is set to a current I _b1 smaller than I _th1 as shown in (C), and I ₂ is set to 0 smaller than I _{th2 as} shown in (D). Therefore, the semiconductor laser does not oscillate. Further, the spontaneous emission light from the electrode 5 is zero because the active layer region of the electrode 6 absorbs light.

Next, at time t ₁ , as shown in (B), the light output is output for a pulse width t _a corresponding to “1”, but as shown in (C), time t _a precedes. I ₁ is set to a current at which a predetermined optical output larger than the threshold current I _{th1 is generated} . At this time, as shown in (D), since I ₂ remains 0, the laser does not oscillate in the entire semiconductor laser because the active layer region of the electrode 6 absorbs light. Further, also in this case, since the active layer region of the electrode 6 absorbs light, the spontaneous emission light toward the end face coat 10 is zero.

Next, the I ₂ laser oscillates is set to the current I _th2 larger than a predetermined light output exits the 0, from the end surface coating 10 side as shown in (B) in t ₁ as shown in (D) Outputs light. At this time, similarly to the first embodiment, the oscillation delay time is significantly reduced as compared with the conventional example, and the light output is quickly generated. Then, "1" when the optical output "0" after the corresponding optical pulse width t _a that in, and (C), I _b1 less than the threshold current I ₁ as shown in (D), I ₂ is 0. Here, I ₁ needs to be less than the threshold current as in the first embodiment.

The same applies to the following. When light having a pulse width of 2 t _a corresponding to “2” is output at t ₂ , I ₁ is larger than the threshold current I _th1 by t _a preceding it. A pulse width of 3 t _{a is} set to _a current at which a predetermined light output is output, I ₂ is set to _a predetermined current larger than a threshold current I _th2 at t ₂ and a pulse width of 2 t _{a is} set, and I ₁ at t ₂ +2 _ta Returns I _b and I ₂ to 0. When light having a pulse width of 3 t _a corresponding to “3” is output at t ₄ , _a predetermined light output greater than the threshold current I _th1 is output by I ₁ preceding that time t _a. The current is set for _a pulse width of 4 t _a , and at t _4, I ₂ is set to _a predetermined current greater than the threshold current I _th2 for a pulse width of 3 t _a , and at t ₄ +3 t _a , I ₁ is I _b1 , I ₂ Returns to 0.

In the case where light having _a pulse width t _a corresponding to “1” is output at t ₅ , the same control as that at time t ₁ is performed.

With the above semiconductor laser driving method, a laser light source in which both the oscillation delay time and the spontaneous emission light emission from the end face are reduced can be realized. In the present embodiment, but the width of the lead time of the I ₁ was t _a, the time width may be any value, not particularly necessary to t _a.

  Needless to say, the control method of the light source device according to the present embodiment can be applied not only to a red light source but also to a blue light source and a green light source. Furthermore, it goes without saying that the laser display device can be similarly adopted.

  A third embodiment according to the present invention will be described with reference to FIG. Here, the example applied to the blue light source of a scanning laser display similarly to Example 1 is described. The configuration of the light source device is the configuration shown in FIG. The light intensity modulation method is the same as that of the first embodiment, but the driving method is different.

In the present embodiment, the semiconductor laser is controlled by a driving method as shown in FIG. 8, and the light intensity is changed by “0120310”. I ₁ is the current injected into the electrode 5 and I ₂ is the current injected into the electrode 6 as in the first embodiment, and the semiconductor laser is oscillated by short-circuiting the electrodes 5 and 6 to inject current. threshold current was a I _th, the semiconductor laser in the entire active layer of the region S ratio of the area S ₁ of the active layer current is injected from the electrode 5 with respect to _t S _{1 /} S multiplied by _t I _th × S when ₁ / S _t is defined as I _th1, and similarly, I _th × S ₂ / S _t multiplied by the ratio S ₂ / S _t of the active layer region S ₂ into which current is injected from the electrode 6 is defined as I _th2 . The same applies to the definition.

In FIG. 8, when the light intensity is initially 0, I ₁ is set to I _th as current I _b1 as shown in (C), and I ₂ is set to 0 smaller than I _{th2 as} shown in (D). Is done. For this reason, the semiconductor laser does not oscillate. In addition, spontaneous emission light from the active layer region of the electrode 5 is absorbed by the active layer region of the electrode 6, so that spontaneous emission light toward the end face coat 10 is also zero. When one light output at _{t 1} (B), the in (C), (D), the larger threshold current I _th1 and _{I 1} and _{I 2} in t ₁ "1" Set to the current at which the optical output is generated. Here, unlike the first embodiment, I ₁ is not preceded because the current of I _th1 equivalent to the threshold current is injected into I ₁ (at time 0) as shown in (C). This is because the oscillation delay time does not occur in the region corresponding to the active layer. Therefore, the oscillation delay time at t ₁ becomes smaller according to the equation (2) than in the prior art, as in the first embodiment.

The light output is set to “2” at t ₂ by the same control method as in the first embodiment. In t _3, and 0 the light output in the 0 to _{I 2} and I ₁ to I _th1. To stop reliably lasing Here, for example, the dotted line in the first half between the half clock I ₁ to I _th1 smaller I _b1 may be set to ((I ₁ of t ₃ -t ₄ shown in C) portion). The latter half of t ₃ -t ₄ is returned to I _th1 . Here, the time width less than the threshold current may not be a particular half clock, may be selected between any length if back to I _th1 by t _4. Between t _{3 and} t ₄ , since I ₂ is 0, spontaneous emission light from the end face coat 10 is 0 as shown in FIG.

Then, to raise the light output "3" at t _4, as well as t _1, may be increased by t ₄ until the current corresponding to the light output of both the I _1, I ₂ "3". At t ₄ , current I _th1 equivalent to the threshold current is injected into I ₁ (in the latter half of t ₃ -t ₄ ) as shown in (C). Since there is no oscillation delay time, it is an oscillation delay time corresponding only to the active layer region of the electrode 6, and an optical output can be obtained with a very small oscillation delay time according to the equation (2). In t _5, may in a similar control manner as in Example 1, the light output I ₁ at t ₅ in the same manner as t ₃ if you the I ₂ to zero I _th1 to zero light output at t ₆ 0 And Here, dotted lines from t ₆ of I ₁ shown in the half clock I _1, for example, to stop the same manner reliably laser oscillation and t ₃ may be set to I _th1 smaller I _b1 ((C) ).

  With the above semiconductor laser driving method, a laser light source in which both the oscillation delay time and the spontaneous emission light emission from the end face are reduced can be realized. Needless to say, this control method can be similarly applied to the pulse width modulation method. Further, it goes without saying that the control method of the light source device of the present embodiment can be similarly applied to the control of light sources of other colors and can be similarly applied to the laser display device.

  A fourth embodiment according to the present invention will be described with reference to FIG. The fourth embodiment shows an example in which the drive control method of the light source device of the present embodiment is applied to a red light source of a scanning laser display. The configuration of the light source device is the same as that shown in FIG. As in the second embodiment, a red semiconductor laser having a wavelength of 635 nm using InGaAlP on a GaAs substrate as an active layer is used as the semiconductor laser. The electrode division of the semiconductor laser is also the same as in the first embodiment. In the present embodiment, the red semiconductor laser is operated by the pulse width modulation driving method as in the second embodiment. However, the control method is different.

FIG. 9 shows the light output and the current control to the electrodes 5 and 6 in the case of the pulse width modulation driving method, and shows an example in which the light intensity is changed by “0120310”. Signal pattern of I ₂ is the same as in Example 2 (D), the light pulses with the same pulse width as I ₂ are output. However, unlike the second embodiment, I ₁ is set to a current value I _J1 at which a prescribed light output is generated before the rise of I ₂ (time t ₀ ) as shown in (C). And I ₁ is decreased only t _a time I _th1 smaller I _b1 corresponding to the same time the threshold current and the fall of I _2. This is because laser oscillation is surely stopped as in the second embodiment. I1 fall time of is a t _a, but the time width may be arbitrary, may not necessarily fall at this time. However, it is necessary to recover to I _J1 before the rising time of the next optical pulse (see (C)). Even with such a control method, laser oscillation does not occur when I ₂ is 0. If I ₂ is greater than I _th2 , any optical output pulse width can be obtained with an extremely small oscillation delay time according to equation (2). be able to.

  With the above semiconductor laser driving method, it is possible to realize a laser light source in which both the oscillation delay time and the spontaneous emission light emission from the end face are reduced. This control method is also applied to the light intensity modulation method. Needless to say, you can. Further, it goes without saying that the control method of the light source device of the present embodiment can be similarly applied to the control of light sources of other colors and can be similarly applied to the laser display device.

  A fifth embodiment according to the present invention will be described with reference to FIG. In the fifth embodiment, the drive control method of the light source device of this embodiment is applied to a blue light source of a scanning laser display. FIG. 10 shows a configuration example of the light source device.

In FIG. 10, reference numeral 4 denotes a semiconductor laser, which is a blue semiconductor laser grown on a GaN substrate in which the p-side electrodes 5 and 6 are divided into two as in the first embodiment. It is desirable that the distance between the first electrode 5 and the second electrode 6 is as close as possible so that there is no region that is not injected into the active layer when a current is passed through both electrodes. On the other hand, if the distance is too close, a leak occurs between the electrodes 5 and 6, but a leak may occur. If there is a problem in control, a part of the p-type semiconductor may be highly insulated by proton implantation or the like. . 7 is an n-side electrode, 8 is an InGaN quantum well active layer, and 9 and 10 are reflective coating films. The reflective coating film 10 has a lower reflectance than the reflective coating film 9 in order to output light output as a light source from the reflective coating film 10. Reference numeral 13 denotes a semiconductor laser driving circuit for driving the n-side electrode 7, and reference numeral 12 denotes a semiconductor switch for connecting between the electrode 6 and the power supply voltage V _DD and controlling conduction / cutoff of current. The electrode 5 is connected to the power supply voltage V _DD . A control circuit 11 controls the semiconductor laser drive circuit 13 and the semiconductor switch 12 based on the image information. A signal based on the image information is input to the control circuit from the outside, but the input signal line is omitted here.

  The concept of the control of the example semiconductor laser in the present example is the same as that described in the first to fourth examples. That is, when the light output is raised from 0 at a desired time, the current to the active layer region of the electrode 5 is drawn from the electrode 7 before the desired time, and when the desired time is not reached at the preceding time. The semiconductor switch 12 is kept cut off so that no current flows in the active layer region of the electrode 6. At this time, the spontaneous emission light from the end surface reflection coat 10 is zero. If the semiconductor switch 12 is turned on for a desired time, light rises with an extremely small oscillation delay time as in the equation (2).

  The difference between the present embodiment and the first to fourth embodiments is that when the semiconductor switch 12 becomes conductive, the current flowing through the active layer of the electrode 5 is reduced by the amount of current flowing through the active layer of the electrode 6. This may be achieved by adjusting the semiconductor laser driving circuit 13 so that the optical output becomes a desired value in a state where the semiconductor switch 12 is conducted. Further, when the laser light is emitted from the state 0, the current from the electrode 7 is set to be less than Ith1 and the semiconductor switch 12 is cut off at least for a certain time as in the first to fourth embodiments. . With the above semiconductor laser driving method, a laser light source in which both the oscillation delay time and the spontaneous emission light emission from the end face are reduced can be realized. Needless to say, this control method can be applied to both the light intensity modulation method and the pulse width modulation method.

1 is a schematic diagram showing an outline of a configuration of a semiconductor laser according to a first embodiment of the present invention. The perspective view of the semiconductor laser of FIG. FIG. 3 is a cross-sectional structure view of the semiconductor laser of the first embodiment when viewed from the light emitting direction. The figure which showed the light intensity modulation system in the 1st Example of this invention. The figure explaining the oscillation delay time of 1st Example of this invention. The figure which shows the system structural example of the laser display apparatus which employ | adopted the 1st Example of this invention. The figure which shows the control system of the light source device which becomes the other Example of this invention. The figure which shows the control system of the light source device which becomes the other Example of this invention. The figure which shows the control system of the light source device which becomes the other Example of this invention. The figure which shows the structural example of the light source device which becomes the other Example of this invention. FIG. 6 is a structural diagram illustrating an example of a conventional laser display device. The figure which shows an example of the light modulation system in a prior art example. The figure which shows the optical output-current characteristic of the semiconductor laser in a prior art example. The figure explaining the oscillation delay time in a semiconductor laser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1R, 1B, 1G, 11 Control circuit 2, 2R, 2B, 2G Semiconductor laser drive circuit 3, 3R, 3G, 3G Semiconductor laser drive circuit 4 Semiconductor laser 5 P side electrode 6 P side electrode 7 N side electrode 8 InGaN Quantum well active layer 9 Reflective coat film 10 Reflective coat film 12 Semiconductor switch circuit 13 Semiconductor laser drive circuit 31 GaN semiconductor substrate 32 n-type AlGaN cladding layer 33 n-type GaN guide layer 34 InGaN guide layer 35 active layer 36 InGaN guide layer 37 AlGaN Electron stopper layer 38 p-type AlGaN / GaN superlattice clad layer 39 p-type GaN contact layer 40 dielectric film 41 p-type electrode 42 n-type electrode 101G semiconductor laser 101B semiconductor laser 101R semiconductor laser 102 lens 103 dichroic mirror 104 dichroic mirror 105 MEMS Mirror 106 Screen 107 Image information processing circuit 108 MEMS drive circuit.

Claims (20)

A method of driving a semiconductor laser comprising a control circuit,
The semiconductor laser includes a resonator structure, an optical waveguide structure provided in the resonator structure for guiding light to be resonated by the resonator structure, an active layer provided in the optical waveguide structure, and the active layer An optical waveguide having a first electrode for injecting current into a partial region of the layer and a second electrode for injecting current into another region of the active layer, the main light output being on the second electrode side In what is emitted from the end face of the structure,
The level of light output of the semiconductor laser is controlled by the current value injected into the first electrode, and the light emission timing of the light output is controlled by the current value injected into the second electrode. A method for driving a semiconductor laser device. In claim 1,
The timing at which the optical output of the semiconductor laser is changed from the light emitting state to the output 0 state is synchronized with the current injected into the first electrode and the current injected into the second electrode. A method of driving a semiconductor laser device, characterized by performing control at a timing of switching to a current value smaller than a predetermined current value at which an optical output is obtained. In claim 1,
When the optical output of the semiconductor laser is 0, the bias current injected into the first electrode is a predetermined value Ib1 smaller than the threshold current, and the bias current injected into the second electrode is low. The predetermined value Ib2 is smaller than the threshold current,
When the light output is increased from 0 to a predetermined light output at a first predetermined time, a current injected into the first electrode at a time preceding the first predetermined time by Δt is set to a predetermined value. While increasing the light output to a predetermined current Ia1 that can be obtained,
A method of driving a semiconductor laser device, wherein the current injected into the second electrode is increased to a predetermined current Ia2 larger than the threshold current in synchronization with the first predetermined time. In claim 1,
When the optical output of the semiconductor laser is 0, the bias current injected into the first electrode is a predetermined value Ib1 smaller than the threshold current, and the bias current injected into the second electrode is low. The predetermined value Ib2 is smaller than the threshold current,
When the light output is increased from 0 to a predetermined light output at a first predetermined time, the current injected into the first electrode at a time preceding the first predetermined time by ta is output as the light output. Is increased to a predetermined current Ia1 to obtain
After the first predetermined time, the current injected into the first electrode is maintained at the value of the current Ia1 for a time width corresponding to a predetermined light output,
In synchronism with the first predetermined time, the current injected into the second electrode is increased to a predetermined current Ia2 larger than the threshold current, and the time is equivalent to the predetermined optical output. A method of driving a semiconductor laser device, characterized by maintaining a current Ia2. In claim 1,
The control for supplying current to the first electrode and the second electrode is a light intensity modulation method synchronized with a clock,
The state of the light output of the semiconductor laser is 0, the first bias current injected into the electrode is a threshold current and the current equivalent I _th1, bias current injected into the second electrode is predetermined Value Ib2,
When the light output is increased from 0 to a predetermined light output at a first predetermined time, a current injected into the first electrode at the first predetermined time is determined to obtain a predetermined light output. Current Ia1 and
A method of driving a semiconductor laser device, wherein the current injected into the second electrode is increased from the predetermined bias current Ib2 to a predetermined current Ia2 in synchronization with the first predetermined time. In claim 5,
When the predetermined light output is set to 0 in the second predetermined time,
A method for driving a semiconductor laser device, wherein a current injected into the first electrode is made smaller than the threshold current for a predetermined time shorter than the clock period from the second predetermined time. The control for supplying current to the first electrode and the second electrode according to claim 1 is a pulse width modulation driving system synchronized with a clock,
When the optical output of the semiconductor laser is 0, the bias current injected into the first electrode is a predetermined value IJ1 larger than the threshold current, and the bias current injected into the second electrode is low. The predetermined value Ib2 is smaller than the threshold current,
When the light output is increased from 0 to a predetermined light output during the first predetermined time, the current injected into the first electrode after the first predetermined time is a time corresponding to the predetermined light output. While maintaining the value of the current value IJ1 by the width,
In synchronism with the first predetermined time, the current injected into the second electrode is increased to a predetermined current IJ2 larger than the threshold current, and the time period corresponding to the predetermined light output is increased. A method of driving a semiconductor laser device, characterized by maintaining a current Ia2. In claim 7, when the predetermined light output is set to 0 in the second predetermined time,
The current injected into the first electrode is made smaller than the threshold current for a predetermined time shorter than the clock period from the second predetermined time, and
A method of driving a semiconductor laser device, comprising reducing an injection current to the second electrode to the bias current Ib2 in the second predetermined time. In claim 1,
The active layer is located between the first conductive type semiconductor layer and the second conductive type layer, and passes through a partial region of the first conductive type semiconductor layer to form a partial region of the active layer. A first electrode for injecting current into the first layer, and a second electrode for injecting current into the other region of the active layer through the other region of the semiconductor layer of the first conductivity type,
When the ratio of the region S1 of the active layer into which current is injected from the first electrode to the region St of the entire active layer is S1 / St, and the first and second electrodes are short-circuited, laser oscillation is performed When the threshold current is Ith,
A method of driving a semiconductor laser device, wherein a bias current Ib1 injected into the first electrode when the optical output is 0 is made smaller than Ith × S1 / St. 2. The active layer according to claim 1, wherein the active layer is located between the first conductive type semiconductor layer and the second conductive type layer, and passes through a partial region of the first conductive type semiconductor layer. A first electrode for injecting current into a partial region of the first electrode, and a second electrode for injecting current into another region of the active layer through another region of the semiconductor layer of the first conductivity type,
When the ratio of the region S1 of the active layer into which current is injected from the first electrode to the region St of the entire active layer is S1 / St, and the first and second electrodes are short-circuited, laser oscillation is performed When the threshold current is Ith,
A bias current Ib1 injected into the first electrode when the optical output is 0 is
A driving method of a semiconductor laser device, characterized in that a threshold current Ith when laser oscillation is performed with the first and second electrodes short-circuited is set to Ith × S1 / St or more. In claim 1,
A method of driving a semiconductor laser element, wherein a bias current Ib2 that is an injection current to the second electrode when the laser beam output is not emitted is set to 0 or less. In claim 1,
The semiconductor laser is
A semiconductor laser in which a third electrode is in contact with a side opposite to the active layer side of the semiconductor layer of the second conductivity type, a laser driving circuit connected to the third electrode, and the second electrode And a semiconductor switch circuit that conducts or cuts off between the power supply voltage or the ground voltage, and a control circuit that controls the laser drive circuit and the semiconductor switch circuit, wherein the first electrode is connected to the power supply voltage or the ground voltage. Connected,
When the optical output is 0, the bias current to the third electrode is a predetermined Ib1, and the laser drive circuit and the semiconductor switch circuit are controlled so that the semiconductor switch is cut off,
When the light output is increased from 0 to a predetermined light output during the first predetermined time, a current injected into the third electrode at the first predetermined time or a time before the first predetermined time is Controlling the laser driving circuit to increase the predetermined bias current Ib1 to a predetermined current Ia1 that provides a predetermined optical output;
Controlling the semiconductor switch circuit such that the semiconductor switch is conductive at a first predetermined time;
Controlling the laser driving circuit to reduce the current to the third electrode to a predetermined bias current Ib1 in the second predetermined time when the predetermined optical output is set to 0 in the second predetermined time; A method of driving a semiconductor laser device, comprising: controlling the semiconductor switch circuit so as to shut off the semiconductor switch circuit. A semiconductor laser, a semiconductor laser driving circuit, and a control circuit;
The semiconductor laser includes a resonator structure, an optical waveguide structure provided in the resonator structure for guiding light to be resonated by the resonator structure, an active layer provided in the optical waveguide structure, and the active layer A first electrode for injecting current into a partial region of the layer, and a second electrode for injecting current into another region of the active layer, wherein the main light output is the light on the second electrode side It is configured to be emitted from the end face of the waveguide structure,
The control circuit controls the level of light output of the semiconductor laser with the current value injected into the first electrode, and the light emission timing of the light output is injected into the second electrode. A semiconductor laser device controlled by value. In claim 13,
The active layer is located between the first conductive type semiconductor layer and the second conductive type layer, and is in contact with the first conductive type semiconductor layer,
The first electrode for injecting a current into a partial region of the active layer through a partial region of the semiconductor layer of the first conductivity type;
A semiconductor laser having the second electrode in contact with the first conductivity type semiconductor layer and injecting a current through the other region of the first conductivity type semiconductor layer into the other region of the active layer; ,
A first laser driving circuit for injecting a current signal into the first electrode;
A second laser driving circuit for injecting a current signal into the second electrode;
And the control circuit for controlling the first and second laser drive circuits,
The control circuit comprises:
The first and second laser drive circuits so that the optical output is 0, the bias current injected into the first electrode is a predetermined Ib1, and the bias current injected into the second electrode is a predetermined Ib2. Control
When the light output is increased from 0 to a predetermined light output during the first predetermined time, the current injected into the first electrode during the first predetermined time or a time before the first predetermined time. Controlling the first laser drive circuit so as to increase the predetermined bias current Ib1 from the predetermined bias current Ib1 to a predetermined current Ia1 at which a predetermined optical output is obtained,
Controlling the second laser driving circuit to increase the current injected into the second electrode from the predetermined bias current Ib2 to the predetermined current Ia2 during the first predetermined time;
When the predetermined optical output is set to 0 in the second predetermined time,
Controlling the first laser driving circuit to reduce the injection current to the first electrode to a predetermined bias current Ib1 in a second predetermined time;
A semiconductor laser device that controls the second laser driving circuit so as to reduce an injection current to the second electrode to the predetermined bias current Ib2. In claim 13,
A semiconductor laser device characterized in that a value obtained by multiplying the ratio S1 / St of the active layer region S1 into which current is injected from the electrode 1 to the region St of the entire active layer of the semiconductor laser is larger than 0.5. In claim 13,
A semiconductor laser in which a third electrode is in contact with the side opposite to the active layer side of the semiconductor layer of the second conductivity type;
A laser driving circuit connected to the third electrode;
A semiconductor switch circuit for conducting or blocking between the second electrode and a power supply voltage or a ground voltage, and a control circuit for controlling the laser drive circuit and the semiconductor switch circuit;
The first electrode of the semiconductor laser is connected to a power supply voltage or a ground voltage,
The control circuit includes:
Controlling the laser drive circuit and the semiconductor switch circuit so that the optical output is 0 and the bias current to the third electrode is a predetermined Ib1, and the semiconductor switch is cut off;
When the light output is increased from 0 to a predetermined light output during the first predetermined time, a current injected into the third electrode at the first predetermined time or a time before the first predetermined time is Controlling the laser driving circuit to increase the predetermined bias current Ib1 to a predetermined current Ia1 that provides a predetermined optical output;
Controlling the semiconductor switch circuit such that the semiconductor switch is conductive at a first predetermined time;
Controlling the laser driving circuit to reduce the current to the third electrode to a predetermined bias current Ib1 in the second predetermined time when the predetermined optical output is set to 0 in the second predetermined time; A semiconductor laser device, wherein the semiconductor switch circuit is controlled to shut off the semiconductor switch circuit. A semiconductor laser corresponding to each color of blue, green, and red as a laser display light source; a semiconductor laser driving circuit and a control circuit corresponding to each of the semiconductor lasers; and an image information processing circuit. In controlling the semiconductor laser drive circuit based on the image information signal of each color,
Each of the semiconductor lasers includes a resonator structure, an optical waveguide structure provided in the resonator structure for guiding light and resonating by the resonator structure, an active layer provided in the optical waveguide structure, A first electrode for injecting a current into a partial region of the active layer; and a second electrode for injecting a current into another region of the active layer, wherein the main light output is the light on the second electrode side. It is configured to be emitted from the end face of the waveguide structure,
The control circuit controls the level of light output of the semiconductor laser with the current value injected into the first electrode, and the light emission timing of the light output is injected into the second electrode. A laser display device controlled by value. In claim 17,
A value obtained by multiplying the ratio S1 / St of the active layer region S1 into which current is injected from the first electrode with respect to the entire region St of the active layer of each semiconductor laser is larger than 0.5. apparatus. In claim 18,
The timing at which the optical output of each semiconductor laser is changed from the light emitting state to the output 0 state is synchronized with the current injected into the first electrode and the current injected into the second electrode. The laser display device is controlled at a timing of switching to a current value smaller than a predetermined current value at which light output can be obtained. In claim 18,
When the optical output of each semiconductor laser is 0, the bias current injected into the first electrode is a predetermined value Ib1 smaller than the threshold current, and the bias current injected into the second electrode is The predetermined value Ib2 is smaller than the threshold current,
When the light output is increased from 0 to a predetermined light output at a first predetermined time, a current injected into the first electrode at a time preceding the first predetermined time by Δt is set to a predetermined value. While increasing the light output to a predetermined current Ia1 that can be obtained,
The laser display device, wherein the current injected into the second electrode is increased to a predetermined current Ia2 larger than the threshold current in synchronization with the first predetermined time.

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