JP6331416B2 - Optical fiber output type laser module - Google Patents

Description

  The present invention relates to an optical fiber output type laser module that emits laser light from an optical fiber.

  In applications such as bioanalysis and image diagnosis using laser light, a noise component included in the laser light appears as noise in the measurement result, so a low noise laser light source is desired. As a method for reducing this optical noise, for example, techniques described in Patent Document 1 and Patent Document 2 are known.

  Patent Document 1 can reduce optical noise by adopting both a high frequency superposition method and APC (Auto Power Control) to control the current of a laser diode.

  According to Patent Document 2, a nonlinear gain change due to the light amount of the semiconductor laser can be compensated by the nonlinear drive unit, and the loop gain of the semiconductor laser drive circuit can be stabilized without being influenced by the light amount of the semiconductor laser. That is, optical noise can be reduced by high-speed APC.

  In addition, the optical noise included in the light emitted from the laser module can be attributed to the laser light source and the electrical noise from the electric circuit that drives the laser. The former includes quantum noise, mode competition noise, Return light noise and the like are known. As the latter, Johnson noise (thermal noise) generated in the device itself, shot noise, flicker noise, switching noise generated as a circuit operation, ground bounce, and the like are known.

  Here, in applications where the light output is sufficiently small compared to the rated output of the laser light source or the light output is variable up to such an area, the light output of the laser light source approaches the threshold value, so that the quantum noise There is a tendency to increase. Further, in such a low output region, the oscillation longitudinal mode becomes unstable, and the influence of mode competition noise increases. In addition, since the noise is present in the electric circuit at a certain level, when these noise components wrap around the laser drive line, the noise level relative to the drive signal level becomes relatively large when the optical output is reduced. Thus, the effect of electrical noise appears greatly.

Japanese Patent No. 2532283 Japanese Patent No. 379086

  The high-frequency superimposition method of Patent Document 1 shows an effect on return light noise, but in applications where the laser light output is varied from the low output region, the optical noise in the low output region can be improved to an increase. I can't. In addition, when the frequency required by the application is a wide band, a high frequency component appears as optical noise.

  Further, in the high-speed APC described in Patent Document 2, since the response speed of the high-speed APC is approximately 10 MHz or less, the intensity of the high frequency component cannot be further reduced in the optical noise.

  An object of the present invention is to provide an optical fiber output type laser module capable of operating in a region where the light output of a laser light source is stable even when the light output is varied, and suppressing an increase in optical noise.

In order to solve the above problems, an optical fiber output type laser module according to the present invention has an optical noise smaller than the predetermined optical noise with respect to a first optical output region having the predetermined optical noise, and A laser light source that emits laser light using a second light output region that is higher in output than the first light output region, a first propagation optical member that propagates light emitted from the laser light source, and the first propagation optics A light branching element that branches light emitted from the member, a light sensor that detects one light branched by the light branching element and converts it into an electrical signal, and a light output detected by the light sensor at a predetermined value. A control unit that controls a drive current for driving the laser light source, a second propagation optical member that propagates a defocused beam by defocusing the other light branched by the light branching element, Said And an optical fiber which enters the defocus beam emitted from the propagation optical member, said second propagation optical member, and adjusting the light output to be incident on the optical fiber to a desired output value.

  An optical fiber output type laser module according to the present invention includes a laser light source that emits laser light, a first propagation optical member that propagates light emitted from the laser light source, and light that is emitted from the first propagation optical member. An optical branching element that branches, an optical sensor that detects one of the lights branched by the optical branching element and converts it into an electrical signal, and the laser light source so that the optical output detected by the optical sensor becomes a predetermined value A control unit that controls a drive current for driving the light, an optical noise detector that detects optical noise from the optical output detected by the optical sensor, and the laser light source and the optical branching element, Adjusting the light quantity by moving the light quantity variable mechanism so that the light noise detected by the optical noise detector is minimized, and the light quantity variable mechanism that varies the light quantity of the laser light from the laser light source. A noise control unit, a second propagation optical member that propagates the other light branched by the light branching element, and an optical fiber that receives the light emitted from the second propagation optical member. To do.

  According to the present invention, there is provided an optical fiber output type laser module that can operate in a region where the light output of a laser light source is stable even when the light output is varied, and can suppress an increase in optical noise. be able to.

It is a figure which shows the structure of the optical fiber output type laser module which concerns on Example 1 of this invention. It is a figure which shows the output dependence of the optical noise in the laser light source of the optical fiber output type laser module which concerns on Example 1 of this invention. It is a figure which shows the structure of the optical fiber output type laser module which concerns on Example 2 of this invention.

  Hereinafter, embodiments of the optical fiber output type laser module of the present invention will be described in detail with reference to the drawings.

Example 1
FIG. 1 is a diagram showing a configuration of an optical fiber output type laser module according to Embodiment 1 of the present invention related to Embodiment 1 of the present invention. This optical fiber output type laser module includes a laser light source 1, propagation optical systems 2 and 6, a beam splitter 3, a photodiode 4, an APC controller 5, and an optical fiber 7.

  As shown in FIG. 2, the laser light source 1 has a first light output region (1 mW to 7 mW in a low light output region) having predetermined optical noise (effective value RMS is approximately 0.28% to 0.37%). On the other hand, a second light output region (having optical noise smaller than the predetermined light noise (effective value RMS is approximately 0.07% to 0.09%) and having a higher output than the first light output region ( The laser light is emitted using 8 mW to 15 mW in the high light output region.

  The propagation optical system 2 (first propagation optical member) propagates the light emitted from the laser light source 1, and includes a lens, an optical fiber, a waveguide, a dimming element, or the like. The beam splitter 3 (light branching element) branches light emitted from the propagation optical system 2.

  The photodiode 4 (light sensor) detects one light branched by the beam splitter 3 and converts it into an electric signal. The APC control unit 5 controls the drive current for driving the laser light source 1 so that the light output detected by the photodiode 4 becomes a predetermined value.

  The propagation optical system 6 (second propagation optical member) includes a lens, an optical fiber, a waveguide, a dimming element, an attenuator, and the like, and propagates the other light branched by the beam splitter 3.

  The optical fiber 7 receives light emitted from the propagation optical system 6. The propagation optical system 6 generates a defocused beam by defocusing light from the beam splitter 3 with a lens or the like, and adjusts the light output incident on the optical fiber 7 to a desired output value.

  Note that at least one of the propagation optical system 2 and the propagation optical system 6 may adjust the light output incident from the propagation optical system 6 to the optical fiber to a desired output value.

  As described above, according to the optical fiber output type laser module of the first embodiment, the laser light source 1 has optical noise smaller than the predetermined optical noise (effective value RMS is approximately 0.07% to 0) as shown in FIG. .09%) and a high output second light output region (8 mW to 15 mW in the high light output region).

  For this reason, from the laser light source 1, for example, optical noise having a high optical output of 10 mW and smaller than predetermined optical noise (effective value RMS is approximately 0.07% to 0.09%) is output. To the beam splitter 3 and the propagation optical system 6.

  The propagation optical system 6 generates a defocused beam by defocusing light from the beam splitter 3 with a lens or the like, and adjusts the light output incident on the optical fiber 7 to a desired output value. That is, the desired optical output required at the output end of the optical fiber 7 is adjusted to 5 mW, for example. Further, smaller optical noise (effective value RMS is approximately 0.07% to 0.09%) is incident on the optical fiber 7.

  Therefore, even when the light output is varied, it is possible to operate in a region where the light output of the laser light source 1 is stable, and an increase in optical noise can be suppressed. Further, a complicated control mechanism is not necessary.

(Example 2)
FIG. 3 is a diagram showing a configuration of an optical fiber output type laser module according to Embodiment 1 of the present invention related to Embodiment 2 of the present invention. This optical fiber output type laser module includes a laser light source 1a, propagation optical systems 2a and 6a, a beam splitter 3, a photodiode 4, an APC control unit 5, an optical fiber 7, a noise control unit 11, a noise detection unit 12, an actuator 21, A knife edge 22 is provided. The APC control unit 5 and the noise control unit 11 are provided in the laser control unit 10.

  Here, since the laser light source 1a, the propagation optical systems 2a and 6a, the noise control unit 11, the noise detection unit 12, the actuator 21, and the knife edge 22 are different from the configuration of the first embodiment, only these configurations will be described.

  The laser light source 1a emits laser light. The propagation optical system 2a propagates the light emitted from the laser light source 1.

  The noise detection unit 12 detects optical noise from the optical output detected by the photodiode 4. The actuator 21 and the knife edge 22 are arranged between the laser light source 1 and the beam splitter 3 and constitute a light amount variable mechanism that varies the light amount of the laser light from the laser light source 1.

  A knife edge 22 is attached to the actuator 21, and when the actuator 21 moves up and down, the knife edge 22 is inserted into the propagation optical system 2a so that the amount of light is adjusted.

  The noise control unit 11 adjusts the amount of light by inserting the knife edge 22 into the propagation optical system 2a by moving the actuator 21 up and down so that the optical noise detected by the optical noise detection unit 12 is minimized.

  As the light quantity variable mechanism, a variable ND (Neutral Density) filter or a variable pinhole can be used instead of the actuator 21 and the knife edge 22.

  According to the optical fiber output type laser module of Example 2 configured as described above, the noise control unit 11 moves the actuator 21 up and down so that the optical noise detected by the optical noise detection unit 12 is minimized. Thus, the knife edge 22 is inserted into the propagation optical system 2a to adjust the light quantity.

  Therefore, even when the light output is varied, it is possible to operate in a region where the light output of the laser light source 1 is stable, and an increase in optical noise can be suppressed. Further, a complicated control mechanism is not necessary.

  The present invention can be used for an optical fiber output type laser module.

DESCRIPTION OF SYMBOLS 1,1a Laser light source 2,2a, 6,6a Propagation optical system 3 Beam splitter 4 Photodiode 5 APC control part 7 Optical fiber 10 Laser control part
11 Noise Control Unit 12 Noise Detection Unit 21 Actuator
22 Knife edge

Claims (1)

A laser using a second optical output region having optical noise smaller than the predetermined optical noise and having a higher output than the first optical output region with respect to the first optical output region having the predetermined optical noise. A laser light source that emits light;
A first propagation optical member for propagating light emitted from the laser light source;
A light branching element that branches light emitted from the first propagation optical member;
An optical sensor that detects one light branched by the optical branching element and converts it into an electrical signal;
A control unit for controlling a drive current for driving the laser light source so that a light output detected by the light sensor becomes a predetermined value;
A second propagation optical member that propagates a defocused beam by defocusing the other light branched by the light branching element;
An optical fiber for receiving a defocused beam emitted from the second propagation optical member,
The optical fiber output type laser module, wherein the second propagation optical member adjusts an optical output incident on the optical fiber to a desired output value.

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