JPH0196629A - Light wavelength conversion module - Google Patents

Abstract

PURPOSE:To realize high wavelength conversion efficiency by using a phased array type laser as a semiconductor laser and then entering a basic wave of high level into a light wavelength converting element. CONSTITUTION:The phased array type semiconductor laser 12 is a semiconductor laser formed by providing stripes closely to one another, and laser light beams 11a, 11b,... which are elliptically sectioned divergent beams are emitted by the stripes 12a, 12b,... formed on an active layer 53 corresponding to, for example, channels 51a, 51b,... and overlap one another deviating slightly in their arrangement direction to form apparently one laser beam 11. Consequently, the basic wave of high level can be entered into the light wavelength converting element 13 and laser light beams emitted by the close stripes 12a, 12b,... are phase-synchronized, so mode hopping is hardly occurred and the tolerance to return light is obtained, so that a noise is hardly generated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention comprises a semiconductor laser and an optical wavelength conversion element that converts the laser light emitted from the semiconductor laser into a second harmonic of 1/2 the wavelength. This invention relates to an optical wavelength conversion module.

(Prior Art) Various attempts have been made to convert the wavelength of laser light (shorten the wavelength) by utilizing second harmonic generation using nonlinear optical materials. Specifically, as an optical wavelength conversion element that performs wavelength conversion in this way, for example, there is a bulk optical device as shown in "Fundamentals of Optoelectronics JA, written by YARtV, translated by Kunio Tada and Takeshi Kamiya (Maruzen Co., Ltd.)". Crystal type, or for example, Journal of the Micro-Optics Research Group of the Optics Conference of the Japan Society of Applied Physics, VOL, 3, No.

2, p28-32 APRIL 25 (198
5), an optical fiber type in which the cladding is filled with a core made of a nonlinear optical material, and furthermore, as shown in Japanese Patent Application Nos. 61-159292 and 61-159293 filed by the present applicant, for example. As described above, a leading waveguide type is known in which a leading wavepath made of a nonlinear optical material is formed between two substrates serving as cladding layers.

The various optical wavelength conversion elements described above are often used in combination with a small and lightweight semiconductor laser to form a module and shorten the wavelength of the laser light emitted by the semiconductor laser.

(Problem to be solved by the invention) However, a general semiconductor laser conventionally used in combination with an optical wavelength conversion element, that is, a single drive type semiconductor laser having only one stripe, has a maximum optical output. However, currently it is only about 50 mW at most, which is extremely small compared to gas lasers and the like. Since the wavelength conversion efficiency of an optical wavelength conversion element is proportional to the optical intensity of the input fundamental wave, a semiconductor laser with such a low optical output is clearly disadvantageous in obtaining a second harmonic with high optical intensity. . This semiconductor laser also has the problem of being susceptible to noise due to the influence of return light from the optical wavelength conversion element. Furthermore, this semiconductor laser also has the problem that mode hopping occurs and the laser light intensity tends to fluctuate unstably. As mentioned above, the wavelength conversion efficiency of the optical wavelength conversion element is proportional to the optical intensity of the fundamental wave input manually, so if the intensity of the laser beam as the fundamental wave fluctuates in this way, the optical intensity of the second harmonic will become extremely high. It becomes unstable.

Therefore, the present invention provides an optical wavelength conversion module that uses a semiconductor laser as a fundamental wave light source, suppresses noise caused by mode hopping and return light, and can obtain a second harmonic with stable high optical intensity. The purpose is to provide

(Means for Solving the Problems) The optical wavelength conversion module of the present invention includes the above-mentioned semiconductor laser and light that converts laser light as a fundamental wave emitted from the semiconductor laser into a second harmonic and emits it. An optical wavelength conversion module comprising a wavelength conversion element is characterized in that a phased array type semiconductor laser is used in place of the conventionally used single drive type semiconductor laser.

(Function) The above-mentioned phased array type semiconductor laser is a type of semiconductor laser in which a plurality of stripes are arranged close to each other, and therefore has an optical output many times higher than that of a single drive type semiconductor laser. According to a semiconductor laser, a fundamental wave with high optical intensity can be input to an optical wavelength conversion element. As described above, the laser beams emitted from a plurality of closely spaced stripes are phase-synchronized, so mode hopping is less likely to occur, and the laser beams are strong against return light and less likely to generate noise.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 and FIG. T42 respectively show the planar shape and side surface shape of the optical wavelength conversion module IO according to the first embodiment of the present invention. This optical wavelength conversion module 1O includes a semiconductor laser 12 that emits a laser beam 11, and an optical wavelength conversion element 1 that converts the wavelength (shortens the wavelength) of this laser beam 11.
3, and an input optical system 14 arranged between them.

As shown in FIG. 3, the semiconductor laser 12 is, for example, p-
An n-GaAs block layer 51 is formed on a GaAs substrate 50, and a plurality of channels 51 a s 51 b s 51 c are formed in this block layer 51 by etching or the like.
The old... is formed, and on this block layer 51 1: p
-AlGaAs cladding layer 52, p-AlGaAs
An active layer 53, an n-AlGaAs cladding layer 54, and an n-GaAs cap layer 55 are sequentially laminated to form a substrate 5o.
A p-electrode 5B is formed on the side, and an n-electrode 57 is formed on the cap layer 55 side. In this configuration, a plurality of stripes 12a, 12b are formed in the active layer 53 corresponding to the channels 51a, 5tb, 51c...
From S12c..., laser beams 11as fibs llc are each a diverging beam with an elliptical cross section.
...is emitted.

Note that FIG. 2 only shows the beam shape of the laser beam 11a.

Each of the above laser beams tta% ttb, llc, old,
* are in a state where they are slightly shifted from each other in the direction of arrangement and overlap each other, so that the semiconductor laser 12 apparently emits one laser beam 11. This laser beam 1
1 is a plurality of laser beams 118% 11b as described above,
Since it is a composite of llc..., the light intensity is extremely high compared to the laser light emitted from a single drive type semiconductor laser. Also, these laser beams 11as llb.

11c... is stripe 12aS12b=
12c... are close to each other, so that they are in positional synchronization with each other.

On the other hand, as an example, the optical wavelength conversion element 13 has a core 1B made of a nonlinear optical material in a hollow part at the center of the cladding 15.
It is an optical fiber filled with As the nonlinear optical material, it is preferable to use an organic nonlinear optical material whose nonlinear optical constant is significantly larger than that of an inorganic material. As this organic nonlinear optical material, for example, JP-A-60-25
No. 0334 and “Nonlner 0ptical
Properties or Organie and
Po1y＊er1c Materials″AC
8SYMPOSIUM 5ERIES 233, D
avldJ, edited by Wllllams (Amer
ican Chemical 5oc1etyS1
MNA (2-methyl-4-nitroaniline) shown in "Organic Nonlinear Optical Materials" supervised by Masao Kato and Hebe Nakanishi (CMC, published in 1985), etc.
, mNA (methanitroaniline), POM (3-methyl-4-nitropyridine-1-oxide), urea, and the like. For example, MNA has a wavelength conversion efficiency that is about 2000 times higher than LiNbO3, which is an inorganic nonlinear optical material, so if the core 1B is formed from this organic nonlinear optical material, an infrared laser can be converted from a small and low-cost semiconductor laser. By using light as a fundamental wave and generating second harmonics, it is also possible to obtain short wavelength laser light in the blue region. On the other hand, the cladding 15 is made of a material having a lower refractive index than the nonlinear optical material. This optical wavelength conversion element 13 has one end surface 13a that is connected to the input optical system 1.
The semiconductor laser 12 is disposed so as to face the semiconductor laser 12 via the semiconductor laser 4 . The input optical system 14 converts the semiconductor laser 12 into an optical wavelength conversion element! A focusing lens 17, a cylindrical lens 18, and an objective lens 19 are arranged in this order on the third side.

Regarding the method of producing a fiber-type optical wavelength conversion element by forming a single-crystalline core from an organic nonlinear optical material such as MNA, see, for example, Japanese Patent Application No. 1983 filed by the present applicant.
A detailed explanation is given in the specification of No.-32914.

In the optical wavelength conversion module 1O described above, the laser beam 11 as the fundamental wave emitted from the semiconductor laser 12
In the vertical plane, the beam is converted into a parallel beam by a focusing lens 17 as shown in FIG. 1, passes through a cylindrical lens 18 as it is, and is focused by an objective lens 19. On the other hand, in the horizontal plane, as shown in FIG. 2, the laser beam 11 is focused by the focusing lens 17 and then diverged, converted into a parallel beam by the cylindrical lens 18, and focused by the objective lens 19. As described above, the laser beam 11 is focused into a small beam spot with a diameter of, for example, about 3 μm. This focused laser beam 11 is irradiated onto the core end surface tea of the optical wavelength conversion element 13. This laser beam 11
The light enters the core IB from ea, and is converted into a second harmonic of 11° with a wavelength of 172 by the aforementioned nonlinear optical material constituting the core 1B. This second harmonic 11° is repeatedly totally reflected between the surfaces of the cladding 15 and travels within the optical wavelength conversion element 13. For example, the phase matching is based on the fundamental wave 11
(in the case of so-called Cerenkov radiation) is taken between the waveguide mode in the core part of the wave and the radiation mode of the second harmonic 11' to the cladding part.

A beam 11'' including the second harmonic 11' is emitted from the other end surface tab of the optical wavelength conversion element 13. This emitted beam 11'' is passed through a filter (not shown), and only the second harmonic ll° is extracted. and used.

As mentioned earlier, phased array semiconductor laser 1
2, it is possible to obtain an extremely high optical output, for example about 2.5 W in continuous drive, compared to a single drive type semiconductor laser, so the optical intensity of the fundamental wave can be made sufficiently high to improve the wavelength conversion efficiency. can be raised. For example, when a pulse-driven laser beam 11 of about 1.5 W and a wavelength of 840 nm is converted into a parallel beam by the input optical system 14 as shown in FIG.
It is also possible to obtain As a result, the second harmonic 11' having sufficiently high optical intensity can be obtained. Also, the stripe of the phased array semiconductor laser 12 is 128%.
The laser beams 11a%llb, llc, etc. emitted from the laser beams 12b, 12c, etc. are phase-locked with each other, so mode hopping is difficult to occur, and noise due to return light is prevented. is also difficult to occur.

Although an embodiment using a fiber type optical wavelength conversion element has been described above, the optical wavelength conversion module of the present invention can also be constructed using a leading waveguide type optical wavelength conversion element.

For example, in the optical wavelength conversion module 20 of the second embodiment shown in FIG. 4, an optical wavelength conversion element 23 in which a three-dimensional leading waveguide 22 is formed on one surface side of a substrate 21 is used. This three-dimensional optical waveguide 22 is formed from the above-mentioned nonlinear optical material, and converts the incident fundamental wave U into a second harmonic. In this embodiment, a phased array semiconductor laser 12 and an input optical system 14 similar to those in the first embodiment are used, and the laser beam 11 focused into a small beam spot is directed to the leading waveguide end face 22a. The light is irradiated and enters the leading waveguide 22 .

Further, FIG. 5 shows an optical wavelength conversion module 30 according to a third embodiment of the present invention, in which a slab-type optical waveguide is used as an optical wavelength conversion element.

The optical wavelength conversion element 31 in this embodiment has a slab-type leading waveguide 34 made of a nonlinear optical material formed between a pair of substrates 32 and 33. At one end of the optical wavelength conversion element 30, a linear diffraction grating (Li
near Grating Coupler) 35
A condensing diffraction grating 36 for emitting a second harmonic wave is provided on the surface of the substrate 32 on the other end side of the tip wavelength conversion element 30 .

The laser beam 11 as a fundamental wave emitted from the phased array type semiconductor laser 12 is converted into a parallel beam by a collimator lens 37, and then collimated into a parallel beam by a collimator lens 37.
5 is irradiated. As a result, the laser beam ti is
It is diffracted by this diffraction grating 35 and enters the leading waveguide 34,
The waveguide 34 made of nonlinear optical material converts the signal into a second harmonic ll'.

This second harmonic wave 11' propagates through repeated total reflection between the outer surfaces of the substrates 32 and 33, is diffracted by the condensing diffraction grating 3B, and is emitted to the outside of the element 30 while being focused.

In the second and third embodiments described above, the phased array semiconductor laser 12 as described above is used as a light source that emits the fundamental wave, and thereby the same effect as that described in the first embodiment is achieved. , the effect can be obtained.

(Effects of the Invention) As explained in detail above, in the optical wavelength conversion module of the present invention, by using a phased array type semiconductor laser, a fundamental wave with an extremely high intensity compared to the conventional one can be transmitted to the optical wavelength conversion element. High wavelength conversion efficiency can be achieved by making it incident on the wavelength. In addition, mode hopping of the semiconductor laser and noise caused by return light are suppressed, so this optical wavelength conversion module has a higher light intensity than a conventional optical wavelength conversion module that uses a semiconductor laser as a light source. is sufficiently high and a stable second harmonic can be obtained.

[Brief explanation of the drawing]

1 and 2 are a side view and a plan view, respectively, of an optical wavelength conversion module according to a first embodiment of the present invention. FIG. 3 is a perspective view showing a semiconductor laser used in the present invention. 5 shows the second embodiment and the third embodiment of the present invention, respectively.
FIG. 2 is a perspective view showing an optical wavelength conversion module according to an example. 1O120,30... Optical wavelength conversion module 11...
・Laser light 11'...Second harmonic 12...
Phased array semiconductor laser 13.23.31・
...Light wavelength conversion element 14...Incidence optical system 15...
Cladding 1B...Core 17...Focusing lens 18...Cylindrical lens 19...Objective lens 21.32.33...Substrate 22.34.
... Optical waveguide 35 ... Linear diffraction grating 8B for fundamental wave input ... Condensing diffraction grating 37 for second harmonic output ...
collimator lens

Claims (1)

[Claims] In an optical wavelength conversion module consisting of a semiconductor laser that emits a laser beam, and an optical wavelength conversion element that converts the laser beam as a fundamental wave emitted from the semiconductor laser into a second harmonic and emits it, the semiconductor laser may be a phased laser. An optical wavelength conversion module characterized in that an array type module is used.