JPH01312529A - Nonlinear optical element - Google Patents

Abstract

PURPOSE:To facilitate miniaturization and stabilization by providing a lens consisting of a nonlinear optical material in a resonator consisting of two reflecting mirrors, a condensing optical system which excites light to the resonator and a coherent light source. CONSTITUTION:The lens 5 consisting of the nonlinear optical material in the resonator consisting of the two reflecting mirrors 3, 4, the condensing optical system 2 which excites light to the resonator and the coherent light source 1 are provided. The light emitted from the light source 1 is resonated by using the two reflecting mirrors 3, 4 and the lens 5 consisting of the nonlinear optical material as the light which condenses in the case of the forward wave and as the light which diverges once and is again condensed by the lens 5 in the case of the backward wave 1. Since the second higher harmonic wave is generated only by the forward wave of the high energy density, the nonlinear optical element is stably operated and is miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a nonlinear optical element used in the fields of communication, optical information processing, optical processing, and optical application measurement and control using lasers.

2. Description of the Related Art Conventional nonlinear optical elements include, for example, a sheet.
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OE L I-4SEE' 88. O'Antlers, 10-17. Shyannuary, 1
988. H'-H-898-18 (C, D, N
abors, W., J., Kozlovsky, and
R, L, Byer, 'Efflc1ent 5eco
nd harmonic generator
of a dlode-pumped cm
Nd:YAGlaser using an
externally resonant cav
lty'', 0-E LASE'88.Los An
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er898-18). FIG. 7 shows a basic configuration diagram of this conventional nonlinear optical element, in which 21 is a coherent light source, 22 is a condensing optical system, 25 is a nonlinear optical crystal, 23 and 24 are reflective films, and 26 is the top surface of the crystal. , 27 are optical paths.

In the conventional light emitting element configured as described above, the light emitted from the coherent light source 21 is collected by the condensing optical system 2.
The light reflected by the reflective film 24 is focused by the crystal upper surface 2 and transmitted through the reflective film 23 to reach the reflective film 24.
6, it is totally reflected and reaches the reflective film 23, and then goes to the reflective film 24 again. By repeating the above steps, the light is made to resonate. If the crystal direction is controlled so that the fundamental wave and the second harmonic are phase-matched only in the optical path from the reflective film 23 to the reflective film 24 within the resonator, the second harmonic is generated only in this part, resulting in high efficiency. It becomes a resonator-type nonlinear optical element that generates a second harmonic.

Problems to be Solved by the Invention In the above configuration, the forward wave and the backward wave take asymmetrical optical paths and resonate, which requires complicated and highly accurate polishing. Furthermore, in order to achieve phase matching between the fundamental wave and the second harmonic, it is necessary to control the wavelength of the light source and the temperature of the crystal, resulting in a lack of stability.

Furthermore, there is a limit to miniaturization due to the bulk structure.

In view of the above points, it is an object of the present invention to provide a small and stable nonlinear optical element with a structure that does not require complicated and highly accurate polishing.

Means for Solving the Problems: A resonator made of two reflecting mirrors, a lens made of a nonlinear optical material placed in the resonator, a condensing optical system for exciting light into the resonator, and a coherent light source. This is a nonlinear optical element characterized by: In addition, a substrate having a nonlinear optical effect, a slab waveguide prepared on the substrate, a lens formed on the slab waveguide, a reflective film formed on both ends of the slab waveguide, and light passing through the slab waveguide. This is a nonlinear optical element characterized by comprising a condensing optical system for excitation and a coherent light source.

According to the above-described configuration, the present invention uses two reflecting mirrors and a lens made of a non-linear optical material to collect light emitted from a coherent light source, condensing the light for forward waves and diverging once for backward waves. The light is refocused and resonates. Second harmonics are generated only by forward waves with high energy density. With the above configuration, a second harmonic generation resonator can be configured with two reflecting mirrors and a lens made of a nonlinear optical material, and a nonlinear optical element can be manufactured without requiring complicated and highly accurate polishing.

In addition, by creating two reflective films and a lens on a slab waveguide formed on a substrate made of nonlinear optical material,
There is no need to phase match the fundamental wave and the second harmonic, and the nonlinear optical element operates stably. Furthermore, by fabricating two reflective films and a lens on the waveguide, the nonlinear optical element can be made smaller.

Example (Example 1) Fig. 1 shows a configuration diagram of a nonlinear optical element in a first example. This is a nonlinear optical element that includes a lens, a condensing optical system that excites light into the resonator, and a coherent light source. In FIG. 1, 1 is a Nd:YAG laser with a wavelength of 1.064 um, 2 is a condensing optical system, and 3 and 4 have a transmittance of 0.00 for light with a wavelength of 1.084 um.
3%, transmittance 90% for light with a wavelength of 0.532 um.
The dielectric reflecting mirror 5 is a lens made of KTP crystal, which is a nonlinear optical material.

The operation of the nonlinear optical element of the first embodiment configured as described above will be described below. Wavelength 1, (H4
The light emitted from the um Nd:YAG laser 1 is condensed by a condensing optical system 2, transmitted through a dielectric reflector 3, the forward wave is condensed, and the backward wave is diverged once and passes through the lens 5. The light becomes condensed, is reflected by the dielectric reflecting mirror 4, and becomes a forward wave again. By repeating the above steps, the light resonates. The light resonance conditions are determined by adjusting the positions of the two reflecting mirrors and the lens. The second harmonic with a wavelength of 0.532% m is generated in the lens portion by a forward wave with high energy density and is transmitted through the dielectric reflecting mirror 4. The conversion efficiency of the second harmonic was 60% with respect to the incident light intensity of 40r*W.

As described above, according to this embodiment, a resonator-type nonlinear optical element with a configuration that does not require high-precision polishing is created using a coherent light source, a focusing optical system, a lens made of a nonlinear optical material, and two reflecting mirrors. was configured.

FIG. 2 is a configuration diagram of a nonlinear optical element showing an embodiment of the tube 2 of the present invention. In the figure, 1 is a Nd: YAG laser with a wavelength of 1°084% m, 2 is a focusing optical system, and 3.4 is a wavelength! , H4um, and has a transmittance of 80% for light with a wavelength of 06532uI11, and is similar to the configuration shown in FIG. The difference from the first configuration is that instead of the lens made of a nonlinear optical effect material, a lens 6.8 and a nonlinear optical crystal are used.
The point is that KTP crystal 7 with - is used.

The operation of the nonlinear optical element of the second embodiment configured as described above will be explained below. A nonlinear optical element was formed by using a lens 6.8 and a nonlinear optical material 7 between the reflecting mirror 3.4. The conversion efficiency of the second harmonic was 30% for an incident light intensity of 40 mW.

According to this example configured as described above, a nonlinear optical element could be formed without adding complicated processing to the nonlinear optical material.

FIG. 3 is a configuration diagram of a nonlinear optical element showing an embodiment of the tube 2 of the present invention. In the same figure, 1 is N with a wavelength of 1°H4um.
d: YAG laser; 2 is a condensing optical system; 5 is a lens made of KTP crystal, which is a nonlinear optical material; the above structure is the same as that shown in FIG. The difference from the first configuration is that
3.4 instead of a reflecting mirror, 0.3% for light with a wavelength of 1.0B4um, and 9 for light with a wavelength of 0.532%m.
The point is that a concave dielectric reflector 9 and a convex dielectric reflector 10 having a transmittance of 0% are used.

The operation of the nonlinear optical element of the second embodiment configured as described above will be explained below. By using two concave and convex reflectors, the resonator length could be shortened.

As described above, according to this embodiment, by shortening the resonator length, it was possible to downsize the nonlinear optical element.

In the first embodiment, the lens was made of KTP crystal, but the lens may be made of other nonlinear materials.

(Example 2) FIG. 41 shows a configuration diagram of a nonlinear optical element in a fourth example, in which a substrate having a nonlinear optical effect, a slab waveguide fabricated on the substrate, and a slab waveguide formed on the slab waveguide. The present invention is a small and stable nonlinear optical element that includes a formed lens, a reflective film formed at both ends of the slab waveguide, a condensing optical system that excites light into the slab waveguide, and a coherent light source. In Fig. 4, 11 is a semiconductor laser with a wavelength Q of 84 ua+, 12 is a focusing optical system, and 13.14 is a wavelength of 0.8
Dielectric reflective film with a transmittance of 0.3% for light with a wavelength of 4%m and a transmittance of 90% for light with a wavelength of 0.42%m, 15 is T
A lens formed of an lO2 film, 16 a LINbOs substrate made of a nonlinear optical material, and 17 a proton exchange slab waveguide.

The operation of the nonlinear optical element of this embodiment configured as described above will be described below. Light emitted from the semiconductor laser 11 with a wavelength of 0°84% m is focused by a focusing optical system 12 and transmitted through a reflective film 13 . The forward wave is condensed light, and the backward wave is diverged once, becomes condensed light by the lens 15, is reflected by the reflective film 14, and becomes a forward wave again.

By repeating the above steps, the light resonates.

The light resonance conditions are adjusted by the positions of both end faces and the lens.

The second harmonic with a wavelength of 0.42% m is generated only by forward waves with high energy density and is transmitted through the reflective film 14. The conversion efficiency of the second harmonic is 5 for an incident light intensity of 40 mW.
It was 1%. In addition, the change in output light intensity with respect to a temperature change of 10 to 50°C is less than 8%, and the change in output light intensity with respect to a wavelength variation of ±20 nm of the semiconductor laser 11 with a wavelength of 0.84 υm is less than 10%. there were.

As described above, according to this embodiment, a coherent light source, a condensing optical system, a substrate made of a nonlinear optical material, a slab waveguide fabricated on the substrate, a lens formed on the slab waveguide, and the slab waveguide By using reflective films formed on both ends of the resonator-type nonlinear optical element, a resonator-type nonlinear optical element was constructed that did not require complicated and highly accurate crystal processing. Furthermore, by using a waveguide structure, the nonlinear optical element could be made smaller.

Furthermore, by using a waveguide structure, there was no need to phase match the light waves of the nonlinear optical element, and the element operated stably.

FIG. 5 is a configuration diagram of a nonlinear optical element showing a fifth embodiment of the present invention. In the same figure, 11 is a wavelength of 0.84u++
+ semiconductor laser, 12 is a focusing optical system, 13.14 is a transmittance of 0.3% for light with a wavelength of 0.84 um, and a wavelength of 0.4
A dielectric film with a transmittance of 90% for light of 2u11, 17
is a proton exchange waveguide, and the above structure is similar to that shown in FIG. The difference from the fourth configuration is that instead of the substrate made of 16 nonlinear optical materials, the optical material is LINbO.
The point is that the lens 18 is formed using a thin film made of a nonlinear optical material MNA instead of the lens 15 using the s-substrate.

The operation of the nonlinear optical element of the fifth embodiment configured as described above will be explained below. The forward wave propagating through the slab waveguide generates a second harmonic at the lens 18 made of a nonlinear optical material. Since MNA can be processed using thin film forming technology, thin film lenses can be easily produced.

As described above, according to this example, a nonlinear optical element could be easily manufactured using thin film formation technology.

FIG. 6 is a configuration diagram of a nonlinear optical element showing a sixth embodiment of the present invention. In the figure, 11 is a semiconductor laser with a wavelength of 0.84 um, 12 is a condensing optical system, and 13.14 is a wavelength of 0.
．． Transmittance 0.3% wavelength 0.42 for 84un+ light
For U++ light, a dielectric reflective film with a transmittance of 90%, 1
5 is a lens formed of a TlO2 film, and 17 is a proton exchange slab waveguide, which has the same structure as that shown in FIG. 4. The difference from the fourth configuration is that both ends of the substrate made of 16 nonlinear optical materials are polished into concave and convex shapes.

The operation of the nonlinear optical element of the sixth embodiment configured as described above will be explained below. By polishing both ends of the substrate into concave and convex shapes, the resonator length could be shortened.

As described above, according to this embodiment, it is possible to downsize the nonlinear optical element.

In the fourth embodiment, the substrate is made of LINbOs, but the substrate may be made of other nonlinear crystals.

Note that in the fourth embodiment, the lens may be a grating lens.

Note that in the fourth embodiment, the lens was fabricated on the waveguide, but the lens may be fabricated inside the waveguide or below the waveguide.

As described in detail, the invention includes a resonator made up of two reflecting mirrors, a lens made of a nonlinear optical material placed inside the resonator, a condensing optical system that excites light into the resonator, and a coherent light source. This makes it possible to fabricate a nonlinear optical element with a structure that does not require complicated and high-precision polishing, thereby increasing its practical effects.

Also, a substrate with a nonlinear optical effect, a slab waveguide fabricated on the substrate, a lens formed on the slab waveguide, a reflective film formed on both ends of the slab waveguide, and a coherent film that excites light to the slab waveguide. By being equipped with a light source and a condensing optical system, it is possible to fabricate a resonator-type second harmonic generation device with a structure that does not require complicated and high-precision polishing, and the device is small and stable. Its practical effects are great because it performs various actions.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a first embodiment of a nonlinear optical element according to the present invention, Fig. 2 is a block diagram of the same element according to another embodiment of the present invention, and Fig. 3 is a block diagram of the same element according to another embodiment of the present invention. Fig. 4 is a block diagram of the fourth embodiment of the nonlinear optical element according to the present invention, Fig. 5 is a block diagram of the same element according to another embodiment of the present invention, and Fig. 6 is a block diagram of the same element according to the present invention. A configuration diagram of the same element in another embodiment, No. 7
The figure is a basic configuration diagram of a conventional nonlinear optical element. lee・Coherent light source, 211・・Condensing optical system, 3
・O・Reflector, 4・φ・Reflector, 5・φ・Lens made of nonlinear optical material, 6・・Coherent light source, 11・
...Condensing light, academic system, 12...Condensing optical system, 13...
Reflective film, 14... Reflection [, 15... Urn lens, 16...
... Substrate made of nonlinear optical material, 17... Slab waveguide. Name of agent Patent attorney Toshio Nakao One idiot Figure 4 Figure 5 Figure 6 Figure Jri Figure 7

Claims (6)

[Claims] (1) A resonator made up of two reflecting mirrors, a lens made of a nonlinear optical material placed in the resonator, a condensing optical system that excites light into the resonator, and a coherent light source. Characteristic nonlinear optical elements. (2) The nonlinear optical element according to claim 1, comprising two lenses and a nonlinear optical crystal. (3) The nonlinear optical element according to claim 1, characterized by comprising a concave reflecting mirror and a convex reflecting mirror. (4) A substrate with a nonlinear optical effect, a slab waveguide fabricated on the substrate, a lens formed on the slab waveguide, a reflective film formed on both ends of the slab waveguide, and an optical waveguide formed on the slab waveguide. A nonlinear optical element characterized by comprising a condensing optical system that excites the light and a coherent light source. (5) Claim 4, characterized by comprising a substrate made of an optical material, a slab waveguide formed on the substrate, and a lens made of a nonlinear optical material formed on the slab waveguide. The described nonlinear optical element. (6) The nonlinear optical element according to claim 4, wherein both end surfaces of the substrate made of a nonlinear optical material are polished so that one side is concave and the other side is convex.