JP2007027372A - Semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To emit stable laser beam. <P>SOLUTION: A semiconductor laser device is provided with a photosensitive element 12a for monitoring beam for detecting the monitoring beam M emitted from the rear end surface 11b of the semiconductor laser element 11, and the photosensitive elements 12b and 12c for stray beam for detection the stray beam at a vicinity of the photosensitive element 12a for monitoring beam. A monitor output compensating unit compensates for the detected result of the photosensitive element 12a for monitoring, on the basis of the detected result of the photosensitive elements 12b and 12c for stray beam, and the drive control unit controls drive of the semiconductor laser element 11, on the basis of the detection result of the compensated monitoring beam so that the output of the semiconductor laser element 11 is constant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device including a semiconductor laser element.

  2. Description of the Related Art A semiconductor laser device that includes a semiconductor laser element and a light receiving element that detects monitor light of the semiconductor laser element, and the semiconductor laser element and the light receiving element are arranged on a stem and sealed with a cap is well known. Such a semiconductor laser device can keep the output amount of the semiconductor laser element constant by controlling the output of the semiconductor laser element based on the detection result of the light receiving element (APC (Automatic Power Control)).

Patent Document 1 discloses a semiconductor laser device that performs APC based on a detection result of a light receiving element that receives reflected light reflected by a window, and the light receiving element is disposed at an inclination from the horizontal. There is disclosed a semiconductor laser device that prevents re-reflected light of reflected light emitted from being emitted from a window.
JP 2004-72072 A

  However, when the light receiving element is irradiated with light other than the laser light emitted from the semiconductor laser element, there is a problem that an accurate output value of the laser light cannot be obtained, and stable and accurate APC cannot be performed. Furthermore, in the case of a semiconductor laser element including a nitride semiconductor, the constituent material of the semiconductor laser element is transparent in the oscillation wavelength of the laser beam to be output and in the visible light region, so that the spontaneous emission light of the semiconductor laser element and the emission of the semiconductor laser element are emitted. Light that has leaked outside the element from a surface other than the end face, laser light that has not been transmitted through the window and reflected by the inner surface of the cap, reflected light from an optical device disposed around the semiconductor laser device, indoor light, etc. The stray light is not absorbed by the semiconductor laser element, but is scattered within the cap and irradiated to the light receiving element. When a large amount of stray light is applied to the light receiving element in this way, the APC cannot be operated accurately, causing the output of the semiconductor laser element to become unstable.

  There is also a method for improving the S / N ratio of the light receiving element by increasing the transmittance of the HR coat on the surface facing the emission end face of the semiconductor laser element and increasing the output of the monitor light. There has been a problem that the output power of the laser beam is reduced.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor laser device that emits a laser beam having a stable output.

  In order to solve the above problems, a semiconductor laser device according to claim 1 includes a semiconductor laser element that emits laser light from an emission end face, and a monitor that is emitted from an end face of the semiconductor laser element that faces the emission end face. In a semiconductor laser device comprising: monitor light detection means for detecting light; and control means for controlling the output of the semiconductor laser element to be constant based on the output of the monitor light detection means. Stray light detection means for detecting stray light in the vicinity, and correction means for correcting the detection result of the monitor light detection means with the detection result of the stray light detection means.

  Here, the monitor light refers to laser light emitted from a surface (rear end surface) facing the emission end surface of the semiconductor laser element. The semiconductor laser element is sealed with a cap having a window that transmits the laser beam emitted from the emission end face to the outside. “Stray light” means spontaneous emission of the semiconductor laser element, emission of the semiconductor laser element. Of the light that has leaked from the surface other than the end face to the outside of the element and the laser light that has exited from the exit end face, the laser light that has been reflected and scattered by the cap inner surface or window without being transmitted through the window, or a semiconductor laser device The reflected light from the optical device arranged in the periphery, the light irradiated inside the cap among the indoor light, and the light scattered inside the cap.

Here, the semiconductor laser element comprising a nitride semiconductor, for _{example, In X Al Y Ga 1-} XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) and this p-type or n-type impurity is doped This means a nitride compound semiconductor laser element containing the prepared material as a constituent element. The semiconductor laser element may have a plurality of transverse modes.

  Monitor light detecting means is arranged near the monitor light detecting means for receiving the monitor light of the semiconductor laser element, and the detection result of the monitor light detecting means is corrected based on the detection result of the stray light detecting means. The stray light component can be subtracted from the detection result, and the amount of monitor light corresponding to the laser light can be obtained. Therefore, the output of the semiconductor laser element can be kept stable.

  Further, when the semiconductor laser element includes a nitride semiconductor, since the constituent material of the semiconductor laser element is transparent in the oscillation wavelength of the laser light and in the visible light region, stray light is not absorbed by the semiconductor laser element, and the monitor light detection means The ratio of the stray light component irradiated becomes large, and it has been difficult to accurately detect the amount of monitor light. Further, when the semiconductor laser element has a plurality of transverse modes, the ratio of laser light and stray light is likely to change. Therefore, it is difficult to accurately detect the amount of monitor light with only the monitor light detection means, and it is difficult to keep the output of the laser light stable. However, by correcting the detection result of the monitor light detection means using the detection result of the stray light detection means, the amount of monitor light corresponding to the laser light can be obtained. Therefore, the output of the laser beam can be kept stable, and the reliability of the semiconductor laser device can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the semiconductor laser device 100. The semiconductor laser device 100 includes a semiconductor laser unit 1, a monitor output correction unit 2, and a drive control unit 3. The semiconductor laser unit 1 includes a semiconductor laser element 11 and a light receiving element 12 mounted on a block 14, a stem 15 that fixes the block 14, and a window 13 that transmits laser light L emitted from the semiconductor laser element 11 to the outside. , A terminal 20 for supplying a driving current to the semiconductor laser element 11, and a detection signal of the light receiving element 12 are represented as wirings 18a, 18b, 18c (hereinafter, collectively referred to as “wiring 18”). ) Via the terminals 17a, 17b and 17c.

  The light receiving element 12 includes three light receiving elements (for example, photodiodes), and the three light receiving elements are connected to wirings 18a, 18b, and 18c, respectively. The wiring 18a is connected to the terminal 17a, the wiring 18b is connected to the terminal 17b, and the wiring 18c is connected to the terminal 17c. The monitor output correction unit 2 inputs the detection signal of the light receiving element 12 from the terminal 17 and corrects the light amount of the monitor light M based on the light amount of the monitor light M and the light amount of stray light. The drive control unit 3 controls the drive current so that the output of the laser light L emitted from the semiconductor laser element 11 is constant based on the light amount of the monitor light whose light amount has been corrected by the output control unit 2, and the semiconductor laser element 11 is supplied with a drive current.

  In the semiconductor laser unit 1, the semiconductor laser element 11, the light receiving element 12, the block 14, and the wiring 18 are hermetically sealed by bonding the edge of the cap 19 and the stem 15 by resistance welding or the like in an inert gas atmosphere. . The terminals 16 and 17 are drawn out through the opening portion of the stem 15.

  The semiconductor laser unit 1 will be described in detail. FIG. 2 is a perspective view of the semiconductor laser unit 1. For convenience, the illustration of the cap 19 is omitted. The light receiving element 12 includes a monitor light receiving element 12a and stray light receiving elements 12b and 12c. The monitor light receiving element 12 a and the stray light receiving elements 12 b and 12 c are arranged on the rear end face 11 b side facing the emission end face 11 a of the semiconductor laser element 11. The monitor light receiving element 12a is disposed on the extended line of the emission axis of the semiconductor laser element 11 so that the light receiving surface faces the rear end face 11b of the semiconductor laser element 11, and the amount of the monitor light M emitted from the rear end face 11b. Is detected.

  The stray light receiving elements 12b and 12c are arranged at positions other than on the extension line of the light emitting axis from the rear end face 11b (positions where the monitor light M is not directly irradiated). For example, the respective light receiving surfaces are received by the monitor light receiving element 12a. It is arranged in the vicinity of the monitor light receiving element 12a so as to be continuously arranged on the surface.

  The stray light receiving elements 12 b and 12 c receive stray light scattered by the cap 19. Further, the monitor light receiving element 12a receives stray light in addition to the monitor light M. The stray light is transmitted from the window 13 among the spontaneous emission light of the semiconductor laser element, the light that is emitted from the surface other than the emission end face of the semiconductor laser element to the outside of the element, and the laser light L emitted from the emission end face. Laser light that is reflected by the inner surface of the cap 19 or the window 13 and scattered inside the cap 19, reflected light from an optical device arranged around the semiconductor laser device 100, or indoor light that is mixed into the cap 19. Say that.

Nitride including semiconductor laser element 11 having In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) and a material doped with p-type or n-type impurities as constituent elements In the case of a compound semiconductor laser element, the semiconductor laser element 11 is transparent with respect to the oscillation wavelength of the laser light L and the visible light region, so that the stray light as described above is not absorbed by the semiconductor laser element 11 and is contained in the cap 19. Scattered. As a result, the ratio of the stray light component in the light received by the monitor light receiving element 12a increases, and the amount of the monitor light M cannot be accurately detected.

  Therefore, by arranging the stray light receiving elements 12b and 12c in the vicinity of the monitor light receiving element 12a, the amount of stray light received by the monitor light receiving element 12a is estimated from the detection results of the stray light receiving elements 12b and 12c. be able to. That is, the light quantity of the monitor light M irradiated to the monitor light receiving element 12a can be obtained by subtracting the light quantity detected by the stray light receiving elements 12b and 12c from the light quantity detected by the monitor light receiving element 12a.

  Returning to FIG. The detection signals of the monitor light receiving elements 12a, 12b, and 12c are output to the monitor output correcting unit 2 via the terminals 17a, 17b, and 17c. The monitor output correction unit 2 calculates an average value from the detection signals of the light receiving elements 12b and 12c. The average value is used as the amount of stray light received by the monitor light receiving element 12a, the average value calculated from the detection signal of the monitor light receiving element 12a is subtracted, and the subtracted value is used as the monitor light amount. Then, the monitor output correction unit 2 outputs the calculated monitor light amount to the drive control unit 3. The drive control unit 3 determines the drive current of the semiconductor laser element 11 based on the monitor light quantity input from the monitor output correction unit 2 so that the output of the laser light L emitted from the semiconductor laser element 11 becomes constant, The drive current is supplied to the semiconductor laser element 11 via the terminal 20 and the wiring 21.

  As described above, the stray light receiving elements 12b and 12c are disposed in the vicinity of the monitor light receiving element 12a that receives the monitor light M of the semiconductor laser element 11, and the detection signals of the stray light receiving elements 12b and 12c are detected. By subtracting the average value from the detection signal of the monitor light receiving element 12a as the amount of stray light received by the monitor light receiving element 12a, the stray light component can be subtracted from the detection signal of the monitor light receiving element 12a. The amount of monitor light M corresponding to L can be obtained. Therefore, the output of the semiconductor laser element 11 can be kept stable.

  In particular, when the semiconductor laser element 11 includes a nitride semiconductor, since the constituent material of the semiconductor laser element is transparent in the oscillation wavelength of the laser light L and in the visible light region, stray light is likely to be scattered in the cap 19 and is received for monitor light. The ratio of the stray light component irradiated to the element 12a is increased, and it is difficult to accurately detect the light amount of the monitor light M. Further, when the semiconductor laser element 11 has a plurality of transverse modes, the ratio of the laser light L and stray light tends to change. Accordingly, the monitor light receiving element 12a alone cannot accurately detect the amount of the monitor light M, and it is difficult to keep the output of the laser light L stable. However, the amount of the monitor light M corresponding to the laser light L can be obtained by correcting the detection result of the monitor light receiving element 12a using the detection results of the stray light receiving elements 12b and 12c. Therefore, the output of the laser beam L can be kept stable, and the reliability of the semiconductor laser device 100 can be improved.

  The contents described above can be changed as appropriate without departing from the spirit of the present invention. For example, the present invention may be applied to a semiconductor laser device including a plurality of semiconductor laser elements. In this case, for each semiconductor laser element, a light receiving element for monitor light is arranged on an extension line of the emission axis of the monitor light. The stray light receiving element may be arranged in the vicinity (on both sides) of each monitor light receiving element, or the stray light receiving element is only received in the vicinity of one of the monitor light receiving elements. An element may be arranged.

  Further, the stray light receiving element may not be arranged on the rear end face 11b side of the semiconductor laser element 11, but may be arranged on the side face side of the semiconductor laser element 11b as shown in FIGS. FIG. 3 is a cross-sectional view of a semiconductor laser device 200 according to another embodiment, and FIG. 4 is a perspective view of the semiconductor laser unit 10. 3 and 4, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 4, the cap 19 is not shown for convenience.

  As shown in FIG. 3, the monitor light receiving element 22 a is arranged on the extended line of the light emitting axis of the semiconductor laser element 11 so that the light receiving surface faces the rear end face 11 b of the semiconductor laser element 11. The stray light receiving element 22b is disposed on the side surface of the semiconductor laser element 11 so that the light receiving surface faces the semiconductor laser element 11 side.

  The detection signal of the monitor light receiving element 22a is input to the monitor output correcting unit 2 via the wiring 28a and the terminal 27a, and the detection signal of the stray light receiving element 22b is input to the monitor output correcting unit 2 via the wiring 28b and the terminal 27b. The monitor output correction unit 2 subtracts a value obtained by multiplying the detection signal of the stray light receiving element 22b by a predetermined value from the detection signal of the monitor light receiving element 22a, and uses the subtracted value as the monitor light amount. Then, the monitor output correction unit 2 outputs the calculated monitor light amount to the drive control unit 3. The drive control unit 3 determines the drive current of the semiconductor laser element 11 based on the monitor light quantity input from the monitor output correction unit 2 so that the output of the laser light L emitted from the semiconductor laser element 11 becomes constant, The drive current is supplied to the semiconductor laser element 11 via the terminal 20 and the wiring 21.

  That is, at least one stray light receiving element may be disposed in a cap including the semiconductor laser element 11. The position of the stray light receiving element is preferably in the vicinity of the position of the monitor light receiving element.

Cross section of semiconductor laser device Perspective view of semiconductor laser section Sectional drawing of the semiconductor laser apparatus in another Example The perspective view of the semiconductor laser part in other Examples

Explanation of symbols

DESCRIPTION OF SYMBOLS 100, 200 Semiconductor laser apparatus 1, 10 Semiconductor laser part 11 Semiconductor laser element 12 Light receiving element 13 Window 14 Block 15 Stem 19 Cap 2 Monitor output correction part 3 Drive control part

Claims (3)

Based on a semiconductor laser element that emits laser light from an emission end face, monitor light detection means that detects monitor light emitted from an end face of the semiconductor laser element that faces the emission end face, and an output of the monitor light detection means In a semiconductor laser device comprising control means for controlling the output of the semiconductor laser element to be constant,
Stray light detection means for detecting stray light in the vicinity of the monitor light detection means;
Correction means for correcting the detection result of the monitor light detection means by the detection result of the stray light detection means;
A semiconductor laser device comprising:   The semiconductor laser device according to claim 1, wherein the semiconductor laser element includes a nitride semiconductor.   The semiconductor laser device according to claim 1, wherein the semiconductor laser element has a plurality of transverse modes.

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