JP2009021432A - Semiconductor laser apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser apparatus capable of controlling the output of an LD light with high accuracy while detecting the Im value. <P>SOLUTION: This semiconductor laser apparatus 1 includes: an LD 3 provided on a LD mounting face 2a on a heat sink 2 provided on an eyelet 5 with turning the rear side R thereof to the eyelet 5; and PD 4 for receiving a light output from an LD 3. This apparatus is characterized in that a laser light output from the LD 3 to a front side F is controlled by monitoring a light received by a PD 4, the PD 4 is provided an inclined plane 2b connected to an LD mounting face 2a which inclines with an angle γ from the eyelet 5 on the heat sink 2 so that a proportion of occupancy of LD light outputted from LD3 in the received light becomes smaller than a proportion that LED light occupies, and a light receiving face 4a of the PD 4 is provided so that it is positioned outside an irradiating region in which a light defined by a divergence angle α of a laser light output from a rear side end R point 203 of the LD 3 is irradiated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device including a light receiving element, and in particular, for an optical disk light source, a medical light source, an illumination light source, a display light source, etc., it is necessary to keep the output constant in a single mode or multimode laser. The present invention relates to a semiconductor laser device used as a light source for a certain application.

  2. Description of the Related Art Conventionally, a semiconductor laser device in which a light receiving element such as a laser diode (LD) and a photodiode (PD) for monitoring laser light (LD light) output to the rear side of the LD is used has been used (for example, Patent Literature). 1 and Patent Document 2). The LD outputs spontaneous emission light (LED light) in addition to LD light.

  A semiconductor laser device described in Patent Literature 1 includes a PD at a position shifted from the optical axis on the rear side of the LD, and includes a single lens and an optical element such as an optical fiber end in front of the LD. Is provided. In this semiconductor laser device, in order to realize accurate monitor output, the PD avoids laser light output from the rear side of the LD, and instead, the laser light output to the front side is reflected by the optical element. It is arranged so that it can enter the PD as reflected light.

The semiconductor laser device described in Patent Document 2 solves the problem that the optical output cannot be accurately controlled due to the difference in the amount of light received between the internal PD inside the device and the external PD outside the device when used as an optical pickup. The internal PD is mounted on the stem so that the light receiving surface of the PD (internal PD) faces the end face of the LD, and the area of the end face facing the internal PD of the LD is reduced.
Japanese Patent Laying-Open No. 2003-229630 (paragraphs 0021-0025, FIG. 1) Japanese Patent Laying-Open No. 2003-60276 (paragraphs 0008, 0021, 0023, FIG. 3)

  Currently, there is a demand for a technique capable of measuring a monitor current value so that LD light is stably output not only at a low output but also at a high output. As the output of LD light increases, higher accuracy is required to monitor LD light. However, the conventional semiconductor laser device has a problem that the accuracy is low because the LD light is monitored by detecting the LD light output from the LD with the PD. The reason is that LD light has a higher light density than LED light. For this reason, even if the LD light output to the front side slightly fluctuates, a current value (hereinafter referred to as an Im value) that flows when the light receiving element receives the light greatly changes. As a result, it is difficult to control so that the LD light is output at a constant level. That is, since the LD light has a high light density, it can be easily detected on the monitor side, but it is not suitable as light used for adjusting the output of the LD light to be constant.

  The present invention has been devised in view of the above-described problems, and an object thereof is to provide a semiconductor laser device capable of accurately adjusting the output of LD light while detecting an Im value.

  In order to solve the above problems, a semiconductor laser device of the present invention includes a laser diode that outputs laser light to a front side and a rear side, and a light receiving element that receives light output from the laser diode, and A semiconductor laser device that adjusts laser light output from the laser diode to the front side by monitoring light received by an element, wherein laser light output from the laser diode is received by the light receiving element The light receiving element is installed such that the proportion of the light emitted from the laser diode is smaller than the proportion of the spontaneous emission light output from the laser diode.

  In particular, in the semiconductor laser device, it is preferable that the proportion of the spontaneous emission light output from the laser diode in the light received by the light receiving element is 60% or more, and the light received by the light receiving element is It is preferable that the ratio of the laser light output from the laser diode is less than 40%. This is because the accuracy of the semiconductor laser device is further improved when the ratio is within this range.

  According to this configuration, the semiconductor laser device adjusts the laser light output from the laser diode to the front side by receiving the spontaneous emission light output from the laser diode by the light receiving element and monitoring it. Here, the light receiving element is a photodiode (PD). The spontaneous emission light (LED light) output from the laser diode has a light density lower than the laser light (LD light) output from the laser diode. Therefore, the current value to be monitored, that is, the absolute value of the current value (Im value) that flows when the light receiving element receives light decreases, so that when the LD light output to the front side fluctuates, The fluctuation is smaller than when the LD light is monitored. This makes it easy to control so that the LD light is output at a constant level, and not only a low-power laser with an output of 50 mW or less, but also a laser with an output higher than 50 mW, or a high-power laser with 100 mW or more. It becomes possible to cope with. Here, the above-mentioned constant means that the fluctuation rate of the Im value is less than 5%.

  In the semiconductor laser device, it is preferable that the light receiving element is disposed so that the spontaneous emission light output from the laser diode hits the light receiving surface of the light receiving element so that the light receiving surface of the light receiving element faces.

  According to this configuration, for example, the semiconductor laser device includes the light receiving element on the rear side from the laser diode, so that the light receiving element can easily avoid receiving the laser light output from the laser diode to the front side. At the same time, the size of the apparatus can be effectively reduced.

  Further, in the semiconductor laser device, the laser diode is disposed on an LD mount surface on a heat sink provided on the eyelet with a rear side facing the eyelet, and the light receiving element is disposed on the heat sink. The light receiving surface of the light receiving element is defined by the spread angle of the laser light output from the rear end surface of the laser diode. It is preferable that the light receiving element is installed so as to be located outside the irradiation region irradiated with the light beam.

  According to such a configuration, the semiconductor laser device can effectively reduce the distance between the light receiving element and the laser diode because the surface on which the light receiving element is disposed is inclined. In addition, according to such a configuration, the semiconductor laser device prevents the laser light output from the end face close to the light receiving element of the laser diode from entering the light receiving surface of the light receiving element, and the spontaneous emission light (LED light) is effective. Light can be received.

  Further, the semiconductor laser device includes a first occupancy ratio indicating a ratio of the directly received laser light among the light received by the light receiving element when the laser diode oscillates at a first laser output value, and the laser diode When the laser beam oscillates at a second laser output value that is 1 to 2 times larger than the first laser output value, the second occupancy ratio indicating the ratio of the directly received laser light among the light received by the light receiving element is 5 respectively. It is preferable that the light receiving element is installed at a position where the difference between the first occupancy and the second occupancy is 1% or less.

  According to such a configuration, when the laser output is increased by 1 to 2 times, the semiconductor laser device has a fluctuation in the proportion of the laser beam directly received in the light received by the light receiving element is 1% or less. The fluctuation of the Im value is stable, and the Im value can be suitably measured even at the time of high output driving.

  Further, the semiconductor laser device includes a first occupancy ratio indicating a ratio of the directly received laser light among the light received by the light receiving element when the laser diode oscillates at a first laser output value, and the laser diode When the laser beam oscillates at a second laser output value 50 mW larger than the first laser output value, the second occupancy ratio indicating the ratio of the directly received laser light among the light received by the light receiving element is 5% or less, respectively. In addition, it is preferable that the light receiving element is installed at a position where a difference between the first occupation ratio and the second occupation ratio is 1% or less.

  According to such a configuration, when the laser output is increased by 50 mW, the semiconductor laser device has a variation in the ratio of the directly received laser light out of the light received by the light receiving element of 1% or less. The fluctuation is stable, and the Im value can be suitably measured even when driving at high output.

  According to the present invention, the semiconductor laser device can detect the Im value mainly by spontaneous emission light (LED light) instead of LD light, and can accurately adjust the output of the front LD light.

The best mode for carrying out the semiconductor laser device of the present invention (hereinafter referred to as “embodiment”) will be described below in detail with reference to the drawings.
(First embodiment)
[Configuration of semiconductor laser device]
FIG. 1 is a perspective view schematically showing the semiconductor laser device according to the first embodiment of the present invention, and FIG. 2 is a plan view of the semiconductor laser device of FIG. 3 is a side view of the semiconductor laser device of FIG. 1 viewed from the X-axis direction, and FIG. 4 is a side view of the semiconductor laser device of FIG. 1 viewed from the Y-axis direction.

  As shown in FIG. 1, the semiconductor laser device 1 according to this embodiment mainly includes a heat sink 2, a laser diode (hereinafter referred to as LD) 3, and a photodiode (light receiving element, hereinafter referred to as PD). 4, an eyelet 5, and an outer lead 6, and adjusts the output of laser light (stimulated emission light, hereinafter referred to as LD light) output from the LD 3 to the front side by monitoring the light received by the PD 4. Is.

  The heat sink 2 is provided on an eyelet 5 and constitutes a stem together with the eyelet 5. The heat sink 2 is provided with an LD 3 and a PD 4. The heat sink 2 is composed of, for example, Cu, Fe, CuW, CuMo, AlN, or AlN plated with Au. The heat sink 2 has an LD mount surface 2a at a portion erected from the eyelet 5, and an inclined surface 2b that is inclined from the eyelet 5 by a predetermined angle γ (see FIG. 3) and connected to the LD mount surface 2a. . Here, in order to reduce the size of the semiconductor laser device 1, the predetermined angle γ is, for example, 5 to 25 °, and preferably 5 to 15 °.

  Note that wires and conductive members, which are internal wirings of the LD 3 and PD 4, are appropriately disposed on the heat sink 2, but are not shown for convenience of explanation. The heat sink 2 is sealed with a cap (not shown) in a nitrogen gas atmosphere, and the cap is formed of a transparent member such as glass in the portion directly above the LD 3.

  The eyelet 5 is a disc having a plurality of holes penetrating the outer leads 6 which are external wirings such as LD3 and PD4, and is made of a metal such as Fe. The outer lead 6 is made of a general electrode metal material made of, for example, a metal such as Cu, Al, Ta, or Cr, an alloy, or the like.

  Although a laser diode (LD) is not specifically limited, For example, it consists of a III-V group compound semiconductor. Specifically, it is made of a compound semiconductor such as GaN, GaAs, GaP, or InP. The LD 3 outputs LD light to the front side F and the rear side R. The ratio of the LD light output to the front side F and the rear side R is such that the ratio of the light output of the front side F is 70% or more. Therefore, the ratio of LD light output to the front side F and the rear side R is 7: 3, 8: 2, 9: 1, or the like. In the light output on the front side F, the ratio of LD light is 90% or more. The LD 3 is disposed on the LD mount surface 2 a via the submount 7 with the rear side R facing the eyelet 5. The ratio of the reflection of the front-side LD light is not particularly limited, but is preferably less than 10% with respect to the output of the front-side LD light.

  For example, the submount 7 includes a thin film circuit in which thin films such as Ti / Pt / Au and Ni / Au are stacked on a substrate. For the substrate of the submount 7, for example, ceramics or a member having high thermal conductivity (AlN, CuW, diamond, SiC) can be used for heat dissipation.

The PD 4 receives light output from the LD 3 and is composed of, for example, a PIN photodiode or PN photodiode using silicon.
In the present embodiment, the light receiving surface 4a of the PD 4 is adjusted so that the proportion of the LD light output from the LD 3 in the light received by the PD 4 is smaller than the proportion of the LED light in the light received by the PD 4. PD4 was installed.
In this PD4, the LD light output from the LD 3 to the rear side R does not substantially hit the light receiving surface 4a, and the LED light (spontaneously emitted light) output from the LD 3 to the rear side R hits the light receiving surface 4a. At the position, it is installed on the inclined surface 2b on the stem 2 so that the light receiving surface 4a faces. Here, “LD light output from the LD 3 to the rear side R does not substantially hit the light receiving surface 4a” refers to at least one of the following three viewpoints.

  In the first aspect of “substantially not hit”, conventionally, a PD is installed within the spread angle of the LD light output from the LD 3 to the rear side R in order to monitor the LD light. In the embodiment, it means that the PD 4 is installed so that the light receiving surface 4a of the PD 4 is not included in the spread angle of the LD light output from the LD 3 to the rear side R.

  Specifically, as shown in FIG. 3, LD light output from the LD lower end point 203 does not enter the light receiving surface end point 201 of the light receiving surface 4 a of the PD 4. That is, PD4 is installed so that it may be located outside the irradiation area defined by the spread angle α of the LD light output from the end surface on the rear side R of LD3. Here, the LD light spreads at an angle of 60 ° to 85 ° in the Y-axis direction (ZY plane) although it depends on the manufacturing conditions of the LD 3. For example, when the angle spreads to about 80 °, the spread angle α shown in FIG. 3 is about 40 °. In addition, LED light spreads to about 160 ° or more, preferably about 180 ° in the Y-axis direction (ZY plane).

  Since the LD light spreads about 40 ° in the X-axis direction (ZX plane), the spread angle β shown in FIG. 4 is about 20 °. In addition, LED light spreads to about 180 degrees in the X-axis direction (ZX plane). Here, in FIG. 4, the light receiving surface end point 201 of the light receiving surface 4 a of the PD 4 is shown as if included in the spread angle in the X axis direction of the LD light output from the LD 3 to the rear side R. However, since the planar positional relationship between the LD 3 and the PD 4 is as shown in FIG. 2, the LD light output from the LD lower end point 203 does not enter the light receiving surface end point 201.

  Further, according to the second aspect of “substantially not hit”, when the LD light output from the LD 3 to the rear side R is 100%, conventionally, the LD light of 90% or more is used to monitor the LD light. In this embodiment, in order to monitor the LED light, the PD 4 is placed at a position where 90% or more, preferably 95% or more, of the LD light output to the rear side R does not hit. Say that it was provided.

  In a third aspect of “substantially not hit”, when the ratio of the LED light to the light detected by the PD 4 is sufficient to adjust the LD light output to the front side, the PD 4 This means that LD light may be included in the light detected. For example, it means that the PD 4 is provided at a position where the proportion of the LED light output from the LD 3 in the light received by the PD 4 is 60% or more. In addition, the PD 4 is provided at a position where the ratio of the laser light output from the LD 3 to the light received by the PD 4 is less than 40%. In particular, it is preferable that the LD light incident from the LD 3 out of all the light detected by the PD 4 is 5% or less, preferably 3% or less.

  Further, in the present embodiment, the first occupancy ratio indicating the proportion of the LD light directly received in the light received by the PD 4 when the LD 3 oscillates at the first laser output value, and the LD 3 is the first laser output value. The second occupancy ratio indicating the proportion of the LD light directly received in the light received by the PD 4 when oscillating with the second laser output value that is 1 to 2 times larger is 5% or less, respectively, and the first occupancy PD4 was installed in the position where the difference between the rate and the second occupation ratio is 1% or less.

  Further, in the present embodiment, the first occupancy ratio indicating the proportion of the LD light directly received in the light received by the PD 4 when the LD 3 oscillates at the first laser output value, and the LD 3 from the first laser output value. The second occupancy ratio indicating the proportion of the LD light directly received in the light received by the PD 4 when oscillating with the second laser output value larger by 50 mW is 5% or less, respectively, and the first occupancy ratio and the first occupancy ratio 2 PD4 was installed in a position where the difference from the occupation ratio was 1% or less.

  According to the semiconductor laser device 1 of the present embodiment, the LED light output from the LD 3 and received by the monitoring PD 4 has a light density lower than that of the LD light, so that the LD light output to the front side fluctuates. In addition, the fluctuation of the Im value is smaller than that in the case where the LD light is monitored. Therefore, it is possible to accurately adjust the output of the LD light from the front side while detecting the Im value. As a result, it is possible to control so that LD light is stably output even at high output.

  As shown in FIG. 3 and FIG. 8, the PD 4 is installed so as to be located outside the irradiation region defined by the spread angle α of the LD light. Here, the length (D) along the hypotenuse from the intersection 501 (see FIG. 8) between the LD mount surface 2a and the inclined surface 2b of the heat sink 2 to the lower end point 502 indicating directly below the upper end point 202 of PD4 is Although depending on the spread angle α of the LD light and the distance (H) between the intersection 501 and the end point 503 of the submount 7, the length (D) is preferably 300 μm or more. The distance (H) between the intersection 501 and the end point 503 of the submount 7 is preferably 200 μm or more.

(Second Embodiment)
[Configuration of semiconductor laser device]
FIG. 5 is a perspective view schematically showing a semiconductor laser device according to the second embodiment of the present invention, and FIG. 6 is a plan view of the semiconductor laser device of FIG. FIG. 7 is a side view of the semiconductor laser device of FIG. 5 viewed from the Y-axis direction. As shown in FIGS. 5 to 7, the semiconductor laser device 1 </ b> A according to this embodiment is configured such that a photodiode (PD) is shifted in the X-axis direction. Accordingly, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. A side view of the semiconductor laser device 1A viewed from the X-axis direction is the same as FIG. In the semiconductor laser device 1A shown in FIG. 5, the PD 4 is disposed farther from the LD 3 than the semiconductor laser device 1 shown in FIG. Therefore, in the light received by the PD 4, the ratio of LD light is reduced and the ratio of LED light is increased. This facilitates control so that the LD light is stably output.

  As mentioned above, although each embodiment was described, this invention is not limited to these, It can implement variously in the range which does not change the meaning. For example, the light receiving surface 4a may be disposed so that the LD light does not hit the light receiving surface 4a of the PD 4 and the LED light output to the front side F hits the light receiving surface 4a. As such an arrangement, there is an arrangement in which the mounting surface of the PD 4 is fixed to a non-transparent portion of the cap (not shown) (the upper portion of the side surface). Further, for example, a reflection surface such as a mirror is formed on the rear side of the LD 3, and the PD 4 is installed at a position where the reflected light reflected by the reflection surface of the LED light output to the rear side R hits the light receiving surface 4a. Good. Note that the thicknesses and lengths of the constituent elements and the like shown in the drawings are exaggerated for clearly explaining the arrangement, and are not limited thereto.

  In order to confirm the effect of the present invention, an experiment was conducted on the semiconductor laser device according to the present embodiment. Specifically, the semiconductor laser device 1 (Example) in which LD3 and PD4 are arranged as shown in FIG. 8 is compared with the semiconductor laser in which LD3 and PD4 are arranged as shown in FIG. Experiments were performed with the apparatus 100 (comparative example).

FIG. 8 is a side view of the semiconductor laser device of the embodiment as viewed from the X-axis direction, and FIG. 9 is a side view of the semiconductor laser device of the comparative example as viewed from the X-axis direction.
The size of the LD 3 was 200 μm in width (X direction) × length (Z direction) 800 μm × thickness (Y direction) 85 μm. In addition, the thickness (Y direction) of the submount was 200 μm.
The size of the PD 4 is such that the main body is horizontal (X direction) 680 μm × vertical (Y direction) 680 μm × thickness (Z direction) 270 μm, and the light receiving surface 4a is (X direction) 500 μm × vertical (Y direction) 500 μm. .
The distance (H) between the intersection point 501 indicating the intersection line between the LD mount surface 2a and the inclined surface 2b of the heat sink 2 and the end point 503 of the submount 7 was set to H = 416 μm.
The inclination angle of the stem 2 in which the PD 4 is disposed is γ = 9 °.

The difference in conditions between the example and the comparative example is as follows.
In the embodiment, the PD 4 is installed so as to be located outside the irradiation region defined by the spread angle α of the LD light, and on the hypotenuse from the intersection point 501 to the lower end point 502 that is directly below the upper end point 202 of the PD 4. The length (D) along the line was D = 372 μm (the distance in the Y-axis direction was about 370 μm).
On the other hand, in the comparative example, the PD 4 is installed so as to be located inside the irradiation region defined by the spread angle α of the LD light, and D = 0 μm. That is, in the comparative example, the distance (L) in the Z-axis direction between the lower end point 502 of the PD 4 and the end point 503 of the submount 7 is made equal to the distance H.
Note that a GaN-based LD is used for the LD 3.

<Ratio of LD light>
As a second aspect of “not substantially hitting” as described above, the ratio of hitting LD light was obtained by simulation. As a result of the simulation, when the LD light emitted from the rear resonance surface of the LD 3 is 100%, the ratio of the LD light entering the PD 4 is 91.5% in the comparative example and only 0.6 in the example. %Met.

<Relationship between monitor output and front laser output>
When the drive current (input current) If of the LD 3 is changed within a predetermined range, the monitor output (Im value) detected by the PD 4 and the output of LD light (front Po) output from the LD 3 to the front side F The relationship was obtained by simulation. The simulation results of Examples and Comparative Examples are shown in FIGS. 10 and 11, respectively. As shown in FIGS. 10 and 11, it can be seen that the front Po can be adjusted by the Im value in both the example and the comparative example.

  In the case of the comparative example, as shown in FIG. 11, when the front Po is 100 [mW], the Im value is about 0.41 [μA]. Further, when the front Po is about 150 [mW], the Im value is about 0.57 [μA]. Therefore, it can be seen that when the Im value fluctuates by about 0.16 [μA], the front Po fluctuates by about 50 [mW].

  On the other hand, in the case of the embodiment, as shown in FIG. 10, when the front Po is about 100 [mW], the Im value is about 0.085 [μA]. When the front Po is about 150 [mW], the Im value is about 0.102 [μA]. Therefore, it can be seen that the front Po changes by about 50 [mW] can be detected when the Im value changes by about 0.017 [μA].

  Analyzing the graphs of FIG. 10 and FIG. 11 in more detail, in the comparative example, since the PD 4 actively receives the LD light on the rear side, it can be seen from the graph of the Im value shown in FIG. I understand. In other words, in the comparative example, when the current value of the drive current If increases from about 40 [mA], the influence of the LD light is added in addition to the LED light, and the Im value rises with a slope similar to that of the front Po ( Note that the values on the left and right axes of the graph are different).

  On the other hand, in the example, it can be seen from the graph of Im value shown in FIG. 10 that since the LD does not oscillate, the PD 4 does not substantially receive the LD light on the rear side. In the embodiment, even if the current value of the drive current If increases from about 40 [mA], the Im value rises only by the LED light without being affected by the LD light. Here, the rate of increase in the Im value in the example becomes moderate. The reason why such a phenomenon occurs is considered as follows. That is, since the LED light is emitted from the entire chip of the LD3, the total amount of the LED light emitted from the entire chip increases as the drive current If increases. The LED light emitted from the entire chip is not uniformly emitted, and the strongest LED light is emitted from the vicinity of the end face ridge closest to the PD 4 (for example, the LD lower end point 203, see FIG. 8). Conceivable. As the drive current If increases, the LED light emitted from the vicinity of the end face ridge changes to LD light and is irradiated in a direction in which the PD 4 cannot receive light. As a result, the amount of LED light entering the light receiving surface 4a of the PD 4 is reduced by the amount of LED light emitted from the vicinity of the end face ridge among the LED light emitted from the entire chip. As a result, it is considered that the Im value changes as shown in FIG. Even if there is such a change, according to the embodiment, the front Po can be adjusted by the Im value.

<Ratio of LD light to light detected by PD>
As a third aspect of the above-mentioned “not substantially hit”, the ratio of the LD light hit to the light detected by the PD 4 was obtained by simulation. The light detected by the PD 4 is evaluated by the current Im [μA] detected by the PD 4. Here, when the front Po is 60 [mW] (first laser output value) (condition 1) and when the front Po is 100 [mW] (second laser output value) (condition 2), The ratio of the rear side LD light, rear side LED light, and other light that affects the current Im [μA] was determined. The simulation results are shown in Table 1. The other light is the remaining light obtained by subtracting the rear LD light and the rear LED light from all the light detected by the PD 4, for example, light reflected by a cap (not shown), etc. Is included.

  As shown in Table 1, in the case of condition 1 (front Po 60 mW), in the comparative example, the ratio of the “rear LD light” that affects the Im value in the light detected by the PD 4 is “70.6. % ”, And the ratio of“ rear LED light ”was“ 17.6% ”. On the other hand, in the example, the ratio of “rear LD light” that affects the Im value in the light detected by the PD 4 is “1.8%”, and the ratio of “rear LED light” is “ 70.0% ". Therefore, in the example, the LD light is not substantially applied to the PD 4. In the example, the influence of other light is higher than that in the comparative example. The other light is reflected light such as LED light other than LED light emitted from the front side LD light or rear side.

  As shown in Table 1, in the case of condition 2 (front Po 100 mW), in the comparative example, the ratio of “rear LD light” that affects the Im value in the light detected by the PD 4 is “74. 0.7% ", and the ratio of" rear LED light "was" 13.3% ". On the other hand, in the example, the ratio of “rear LD light” that affects the Im value in the light detected by the PD 4 is “2.2%”, and the ratio of “rear LED light” is “ 62.4% ". Therefore, in the example, the LD light is not substantially applied to the PD 4.

Further, comparing the condition 1 and the condition 2, in both the comparative example and the example, when the front Po is increased, the ratio of the “rear-side LD light” that affects the Im value of the light detected by the PD 4 is The ratio of “rear LED light” increases and decreases.
As shown in Table 1, the front Po increases from condition 1 to condition 2 by 1.67 times. On the other hand, in the comparative example, the ratio of the “rear LD light” that affects the Im value in the light detected by the PD 4 is “70.6%” in the condition 1 and in the condition 2 Since it is “74.7%”, it is increased by “4.1%”. On the other hand, in the embodiment, the ratio of “rear LD light” that affects the Im value in the light detected by the PD 4 is “1.8%” in the condition 1 and “2. Since it is “2%”, it is increased by “0.4%”. That is, compared with the comparative example, the fluctuation of the ratio of “rear LD light” is 1/10 or less. Therefore, the embodiment has an effect that when the front Po increases, the fluctuation of the Im value can be reduced with respect to the fluctuation of the output of the LD light. As a result, when the front Po increases, the fluctuation of the Im value is stable, and even at the time of high output, it can be accurately adjusted so that the LD light is stably output while detecting the Im value. Note that the ratio of “rear side LED light” in condition 2 is smaller than in condition 1, but the amount of light detected by PD 4 is higher in condition 2 than in condition 1. The absolute value of the rear side LED light detected by the PD 4 is larger in the condition 2 than in the condition 1.

<Im value change with time>
About the Example and the comparative example, the fluctuation | variation of Im value by a time-dependent change was confirmed. The results are shown in FIG. FIG. 12 is a graph showing monitor characteristics according to the elapsed time of the semiconductor laser device in which the Po output is 20 mW in continuous oscillation (CW). The Im value in FIG. 12 is an Im value detected by the PD 4. In this experiment, when 300 hours of continuous operation was performed, the fluctuation of the Im value was obtained every 50 hours with the Im value before the experiment as a reference (100%).

  In the comparative example, the Im value significantly decreased in the first 50 hours, and continued to decrease and became “94.46%” after 300 hours had elapsed. That is, the fluctuation range was “5.34%”. On the other hand, in the examples, the Im value did not decrease and rose “0.72%” when it fluctuated the most, and after 300 hours, it reached “100%”, the same as before use. That is, the fluctuation range was “0.72%”. Therefore, compared to the comparative example, the embodiment has a smaller fluctuation of the Im value due to the change with time, and the laser output on the front side can be accurately adjusted by monitoring the LED light even if it is used for a long time.

  The semiconductor laser device according to the present invention is an optical disc capable of recording / reproducing and recording information such as illumination, exposure, display, various types of analysis, CD / MD / DVD, etc. It can be used in various fields such as systems, medical light sources, laser printers, and optical networks.

1 is a perspective view schematically showing a semiconductor laser device according to a first embodiment of the present invention. FIG. 2 is a plan view of the semiconductor laser device of FIG. 1. FIG. 2 is a side view of the semiconductor laser device of FIG. 1 viewed from the X-axis direction. FIG. 2 is a side view of the semiconductor laser device of FIG. 1 viewed from the Y-axis direction. It is a perspective view which shows typically the semiconductor laser apparatus which concerns on 2nd Embodiment of this invention. FIG. 6 is a plan view of the semiconductor laser device of FIG. 5. FIG. 6 is a side view of the semiconductor laser device of FIG. 5 viewed from the Y-axis direction. It is the side view which looked at the semiconductor laser apparatus of the Example from the X-axis direction. It is the side view which looked at the semiconductor laser device of the comparative example from the X-axis direction. It is a graph which shows the electric current-output characteristic of the semiconductor laser apparatus of an Example. It is a graph which shows the electric current-output characteristic of the semiconductor laser apparatus of a comparative example. It is a graph which shows the monitor characteristic by the elapsed time of a semiconductor laser apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A Semiconductor laser apparatus 2 Heat sink 2a LD mount surface 2b Inclined surface 3 LD (laser diode)
4 PD (photodiode; light receiving element)
4a Light-receiving surface 5 Eyelet 6 Outer lead 7 Submount

Claims (7)

A laser diode that outputs laser light to the front side and the rear side; and a light receiving element that receives light output from the laser diode, and monitors the light received by the light receiving element to thereby move the front side from the laser diode. A semiconductor laser device for adjusting the laser beam output to
The light receiving element is installed such that a ratio of laser light output from the laser diode to light received by the light receiving element is smaller than a ratio of spontaneous emission light output from the laser diode. A semiconductor laser device.   2. The semiconductor laser according to claim 1, wherein the light receiving element is disposed so that a light receiving surface of the light receiving element faces a position where spontaneous emission light output from the laser diode hits a light receiving surface of the light receiving element. apparatus. The laser diode is disposed on the LD mount surface on the heat sink provided on the eyelet with the rear side facing the eyelet.
The light receiving element is disposed on an inclined surface connected to the LD mount surface at a predetermined angle from the eyelet on the heat sink,
The light receiving element is installed such that the light receiving surface of the light receiving element is positioned outside the irradiation region irradiated with the light beam determined by the spread angle of the laser light output from the rear end face of the laser diode. The semiconductor laser device according to claim 2. A first occupancy ratio indicating a proportion of the directly received laser light among the light received by the light receiving element when the laser diode oscillates at a first laser output value; and
When the laser diode oscillates at a second laser output value that is 1 to 2 times larger than the first laser output value, the second occupancy ratio indicating the ratio of the directly received laser light among the light received by the light receiving element is Are less than 5% each,
4. The semiconductor laser device according to claim 3, wherein the light receiving element is disposed at a position where a difference between the first occupancy and the second occupancy is 1% or less. A first occupancy ratio indicating a proportion of the directly received laser light among the light received by the light receiving element when the laser diode oscillates at a first laser output value; and
When the laser diode oscillates at a second laser output value 50 mW larger than the first laser output value, the second occupancy ratio indicating the ratio of the directly received laser light among the light received by the light receiving element is 5 respectively. % Or less,
4. The semiconductor laser device according to claim 3, wherein the light receiving element is disposed at a position where a difference between the first occupancy and the second occupancy is 1% or less.   2. The semiconductor laser device according to claim 1, wherein the proportion of the spontaneous emission light output from the laser diode in the light received by the light receiving element is 60% or more.   2. The semiconductor laser device according to claim 1, wherein a ratio of laser light output from the laser diode to light received by the light receiving element is less than 40%.

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