JP2020027844A - Semiconductor laser device - Google Patents

Abstract

To provide a semiconductor laser device capable of shifting an operating point of current of a semiconductor laser to the high output side and capable of improving an elliptic beam shape peculiar to the semiconductor laser.SOLUTION: A semiconductor laser device comprises: a semiconductor laser 1; a lens 2 for making light of the semiconductor laser 1 be parallel light; a wedge substrate 3 adjusted so that an angle of an incidence surface for the parallel light from the lens 2 with respect to laser light is equal to or larger than a Brewster angle and adjusted so that an angle of an emission surface with respect to the laser light is the Brewster angle; a beam shaping unit 4 for shaping a transmitted beam from the wedge substrate 3; a beam splitter 5 for making a transmitted beam from the beam shaping unit 4 branch; a photo diode 6 for detecting light from the beam splitter 5; and an APC control unit 7 that on the basis of optical output detected by the photo diode 6, controls the semiconductor laser 1 so that the optical output has a predetermined value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor laser device that outputs light of a semiconductor laser.

  In a semiconductor laser device using a semiconductor laser, the operating point of the current of the semiconductor laser may be controlled depending on the application from the viewpoint of stabilizing characteristics.

  A conventional optical fiber output type semiconductor laser device partially blocks a laser beam before being incident on an optical fiber and drives the APC (auto power control) to set the operating point of the semiconductor laser current to a high output side. Has shifted to

JP-A-2015-138927

  However, in the case of a semiconductor laser device that is not an optical fiber output type, since the laser light is partially shielded, the beam shape of the output light of the semiconductor laser device is affected, and the shape of the elliptical beam becomes worse. .

  An object of the present invention is to provide a semiconductor laser device capable of shifting an operating point of a semiconductor laser to a high output side and improving an elliptical beam shape peculiar to the semiconductor laser.

  Claim 1 of the semiconductor laser device according to the present invention is a semiconductor laser, a lens that converts the light of the semiconductor laser into parallel light, and an incident surface on which the parallel light from the lens is incident has a Brewster angle relative to the laser light. A wedge substrate adjusted so as to have a Brewster angle with respect to the laser beam, a beam shaping unit for shaping light transmitted through the wedge substrate, and transmission of the beam shaping unit. A beam splitter for splitting light, a light detecting unit for detecting light from the beam splitter, and controlling the semiconductor laser such that the light output becomes a predetermined value based on the light output detected by the light detecting unit. And a control unit.

  The invention according to claim 2 is characterized in that the wedge substrate has a wedge angle of 5 degrees or more.

  According to the present invention, the wedge substrate is adjusted so that the incident surface on which the parallel light from the lens is incident is not less than the Brewster angle with respect to the laser light, without applying a special coating to the substrate. A reflectance of 10% to 20% can be obtained. Further, the operating point of the semiconductor laser can be shifted to a higher output side by the amount of dimming reflected on the incident surface of the wedge substrate.

  Further, since the emission surface is adjusted to have a Brewster angle with respect to the laser light, the light from the wedge substrate is incident on the beam splitter without being reflected on the emission surface.

  Further, since a wedge substrate is used, the beam width in the horizontal direction can be increased, and the elliptical beam shape of the semiconductor laser can be improved.

FIG. 1 is a configuration diagram of a semiconductor laser device according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating an incident angle, an outgoing angle, and a wedge angle of laser light with respect to a wedge substrate provided in the semiconductor laser device according to the first embodiment of the present invention. It is a figure which shows the reflectance and beam magnification with respect to a wedge angle. FIG. 4 is a configuration diagram of a semiconductor laser device according to a second embodiment of the present invention.

(Example 1)
FIG. 1 is a configuration diagram of a semiconductor laser device according to a first embodiment of the present invention. This semiconductor laser device includes a semiconductor laser 1, a lens 2, a wedge substrate 3, a beam shaping unit 4, a beam splitter 5, a photodiode (PD) 6, and an APC control unit 7.

  The semiconductor laser 1 is excited by carrier injection composed of electrons and holes injected by current driving, and outputs laser light generated by stimulated emission generated when the injected electrons and holes lose carrier pairs.

  The lens 2 is made of glass, plastic, or the like, is arranged to face the semiconductor laser 1, converts the laser light from the semiconductor laser 1 into parallel light, and guides the laser light to the wedge substrate 3.

  The wedge substrate 3 is of a synthetic quartz type, and a slight wedge is provided on the front and back surfaces of the laser to separate reflected beams from the front and back surfaces.

  FIG. 2 shows the incident angle θ1, the emission angle θ2, and the wedge angle α of the laser light with respect to the wedge substrate 3. The wedge angle α is an angle between the entrance surface 3A (front surface) and the exit surface 3B (back surface). The incident angle θ1 is an angle between a normal line perpendicular to the incident surface 3A and the incident light. The emission angle θ2 is an angle between a normal line perpendicular to the emission surface 3B and the emitted light.

(Emission angle θ2−Incident angle θ1) is the beam deflection angle δ, and the beam deflection angle δ can be obtained from Expression (1) using the refractive index n of the wedge substrate 3 and the wedge angle α.
δ = (n−1) α (1)
The input beam width is d1, the output beam width is d2, and the beam magnification is d2 / d1.

  The beam shaping unit 4 shapes light transmitted through the wedge substrate 3. The beam splitter 5 splits the transmitted light of the beam shaping unit 4 into two. The photodiode (PD) 6 corresponds to the light detection unit of the present invention, and detects light from the beam splitter 5.

  The APC control unit 7 corresponds to the control unit of the present invention, and controls the current of the semiconductor laser 1 based on the light output detected by the photodiode (PD) 6 so that the light output becomes a predetermined value.

  Next, the operation of the semiconductor laser device according to the first embodiment thus configured will be described. First, the light emitted from the semiconductor laser 1 is converted into parallel light by the lens 2 and is incident on the wedge substrate 3.

  The wedge substrate 3 is adjusted so that the incident surface on which the parallel light from the lens 2 is incident has a Brewster angle or more with respect to the laser light. A reflectance of ２０20% can be obtained.

  Further, since the emission surface of the wedge substrate 3 is adjusted so as to have a Brewster angle with respect to the laser light, the light from the wedge substrate 3 enters the beam splitter 5 without being reflected on the emission surface.

  Part of the light reflected by the beam splitter 5 is detected by a photodiode (PD) 6. The detected signal is output to the APC control unit 7. The APC controller 7 controls the current of the semiconductor laser 1 based on the light output detected by the photodiode (PD) 6 so that the light output becomes a predetermined value.

  As a result, the operating point of the semiconductor laser 1 is shifted to the high output side by the amount of dimming reflected on the incident surface of the wedge substrate 3, and the characteristics of the semiconductor laser 1 can be stabilized.

  Further, since the wedge substrate 3 is used, the beam width in the horizontal direction can be increased, and the elliptical beam shape of the semiconductor laser 1 can be improved.

  FIG. 3 shows the reflectance and the beam magnification with respect to the wedge angle. Here, it is assumed that the refractive index of the glass material is 1.6 for P polarization. As can be seen from FIG. 3, by setting the wedge angle α to 5 degrees or more, the reflectance becomes 10% or more.

(Example 2)
FIG. 4 is a configuration diagram of a semiconductor laser device according to a second embodiment of the present invention. This semiconductor laser device includes a semiconductor laser 1, a lens 2, wedge substrates 3a and 3b, a beam shaping unit 4, a beam splitter 5, a photodiode (PD) 6, and an APC control unit 7.

  The wedge substrate 3a receives light from the lens 2 and emits transmitted light to the wedge substrate 3b. The wedge substrate 3b receives light from the wedge substrate 3a and emits transmitted light to the beam shaping unit 4.

  The functions of the wedge substrates 3a and 3b are the same as the functions of the wedge substrate 3 of the first embodiment. Therefore, by providing the wedge substrates 3a and 3b, it is possible to obtain a reflectance of 20% to 40% without applying a special coating to the wedge substrates 3a and 3b. Therefore, the effect of the semiconductor laser device of the second embodiment is greater than the effect of the semiconductor laser device of the first embodiment.

  Although the wedge substrate 3 is used in the semiconductor laser devices of the first and second embodiments, a prism having a wedge angle may be used instead of the wedge substrate 3.

  INDUSTRIAL APPLICABILITY The present invention is applicable to general semiconductor laser devices mounted on medical equipment and analytical measurement equipment using laser light.

Reference Signs List 1 semiconductor laser 2 lens 3, 3a, 3b wedge substrate 4 beam shaping unit 5 beam splitter 6 photodiode (PD)
7 APC control unit

Claims (2)

A semiconductor laser;
A lens that converts the light of the semiconductor laser into parallel light,
A wedge substrate adjusted so that an incident surface on which the parallel light from the lens is incident has a Brewster angle or more with respect to the laser light, and an emission surface adjusted to have a Brewster angle with respect to the laser light,
A beam shaping unit that shapes transmitted light of the wedge substrate,
A beam splitter for splitting transmitted light of the beam shaping unit,
A light detection unit that detects light from the beam splitter,
A control unit that controls the semiconductor laser such that the light output becomes a predetermined value based on the light output detected by the light detection unit,
A semiconductor laser device comprising: 2. The semiconductor laser device according to claim 1, wherein the wedge substrate has a wedge angle of 5 degrees or more.

Images