JP2006073549A - External resonator-type wavelength variable optical source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an external resonator-type wavelength variable optical source where a wavelength variable range can be enlarged, an optical axis can easily be adjusted, and miniaturization is possible. <P>SOLUTION: In the external resonator-type wavelength variable optical source, a wavelength is changed by an optical amplifier and a wavelength selection/reflection means arranged outside the optical amplifier. The optical source is provided with first and second optical amplifiers in which non-reflection films are given to one outgoing end and which are different in wavelength ranges; first and second optical waveguides on which outgoing light from one outgoing ends where the non-reflection films of the first and second optical amplifiers are given are made incident; a third optical waveguide connecting light transmitted through the first and second optical waveguides by branching and synthesizing regions; a lens making outgoing light from one outgoing end where the non-reflection film of the third optical waveguide is given parallel; the wavelength selection/reflection means on which outgoing light from the lens is made incident, and in which reflected light is made incident on one outgoing end to which the non-reflection film of the third optical waveguide is given through the lens; and an optical fiber where outgoing light from the other outgoing end, to which the non-reflection film of the third optical waveguide is given is made incident on one end and outgoing light is outputted from the other end. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical resonator and an external resonator type wavelength tunable light source that changes the wavelength by a wavelength selective reflection means disposed outside the optical amplifier, and more particularly, the wavelength tunable range is expanded and the optical axis can be easily adjusted and reduced in size. The present invention relates to a possible external resonator type tunable light source.

  Prior art documents related to an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier include the following.

Japanese Patent Application Laid-Open No. 06-097601 Japanese Patent Laid-Open No. 06-112583 US Patent Registration No. 5594744 Japanese Patent Laid-Open No. 11-251665

  FIG. 9 is a block diagram showing an example of a conventional external resonator type wavelength tunable light source described in “Patent Document 3”. In FIG. 9, 1 is an optical amplifier using a semiconductor laser with an antireflective film on one output end, 2, 4 and 6 are lenses, 3 is an optical isolator that allows light to pass only in a predetermined direction, and 5 is An optical fiber, 7 is a diffraction grating as a wavelength selection element, 8 is a reflector such as a mirror, 9 is a rotation control means, 10 is a rotation drive means such as a motor, and 11 is an optical amplifier drive means. Further, 9 and 10 constitute a wavelength control means 50, and 7 and 8 constitute a wavelength selective reflection means 51, respectively.

  The outgoing light from one outgoing end of the optical amplifier 1 becomes parallel light by the lens 2 and passes through the optical isolator 3. The light transmitted through the optical isolator 3 is collected by the lens 4 and is incident on one end of the optical fiber 5.

  The outgoing light from the other outgoing end of the optical amplifier 1 becomes parallel light by the lens 6 and is incident on the diffraction grating 7. The diffracted light in the diffraction grating 7 is incident on the reflector 8, and the reflected light from the reflector 8 is reflected by the diffraction grating 7, collected by the lens 6, and again incident on the other output end of the optical amplifier 1.

  The reflector 8 is fixed to the rotation driving means 10, and the output of the rotation control means 9 is connected to the control input terminal of the rotation driving means 10. The output of the optical amplifier driving means 11 is connected to the control input terminal of the optical amplifier 1.

  Here, the operation of the conventional example shown in FIG. 9 will be described. The optical amplifier 1 is constituted by a semiconductor laser, and a non-reflective film is applied to one emission end indicated by “NR01” in FIG. 9, and the active layer of the active layer according to the drive current supplied from the optical amplifier drive means 11 is provided. Light in a wavelength region corresponding to the band gap energy is emitted from both emission ends.

  The light emitted from one output end of the optical amplifier 1 on which the non-reflective film is applied is incident on the diffraction grating 7 through the lens 6, and parallel light is incident on the reflector 8 at a diffraction angle corresponding to the wavelength of the incident light. To reflect.

  Then, the reflected light from the reflector 8 is reflected by the diffraction grating 7, collected by the lens 6, and again incident on one output end of the optical amplifier 1.

The optical arrangement of the optical amplifier 1, the diffraction grating 7 and the reflector 8 is called a Littman arrangement. The groove interval of the diffraction grating 7 is "d", the order of the diffracted light is "M", and the normal line of the diffraction grating 7 and the optical amplifier. 1 is an angle (incident angle to the diffraction grating 7) with respect to the outgoing optical axis, and the angle between the normal line of the diffraction grating 7 and the reflected optical axis of the light reflected by the diffraction grating 7 (diffraction from the diffraction grating 7). When the angle) is “β”, the wavelength “λ” selected by the diffraction grating 7 is
λ = d / M · [sin α + sin β] (1)
It is represented by

  The light incident on the optical amplifier 1 from the diffraction grating 7 propagates in the optical amplifier 1 and is reflected by the reflectance of the other emission end not provided with the non-reflective film, propagates in the optical amplifier 1 and is again non-reflective. The light is emitted from one of the emission ends provided with the film.

  Therefore, the light that does not pass through the other output end of the optical amplifier 1 that is not provided with the non-reflective film is configured between the reflector 8 and the other output end of the optical amplifier 1 that is not provided with the non-reflective film. The laser is oscillated by resonating with the resonator.

  On the other hand, the light transmitted through the other emitting end of the optical amplifier 1 that is not provided with the non-reflective film is incident on the optical fiber 5 through the lens 2, the optical isolator 3, and the lens 4 as laser light and used for various measurements. It is done.

  In such a state, when the rotation driving means 10 changes the angle of the reflector 8 around the rotation center indicated by “RC01” in FIG. 9 based on the control signal of the rotation control means 9 constituting the wavelength control means 50, The diffraction angle β of the diffracted light that is perpendicularly incident on the reflector 8 changes, and the wavelength is changed because the laser oscillation occurs at the wavelength obtained from the equation (1). Further, since the resonator length of the resonator formed between the reflector 8 and the other emitting end of the optical amplifier 1 where the non-reflective film is not applied changes, the resonance wavelength also changes.

  As a result, the output light from one output end of the optical amplifier 1 on which the non-reflective film is applied is incident on the diffraction grating 7, and the diffracted light of the diffraction grating 7 is reflected again on the diffraction grating 7 by the reflector 8. The light returned from the diffraction grating 7 is disposed so as to be incident on one emission end of the optical amplifier 1 on which the non-reflective film is applied, and the reflector 8 and the other on which the non-reflective film of the optical amplifier 1 is not applied. The wavelength of laser oscillation can be changed by constituting a resonator with the emission end of the laser beam and changing the angle of the reflector 9 by the wavelength control means 50.

  In addition, the optical arrangement of the optical amplifier 1, the diffraction grating 7, and the reflector 8 is set to the Littman arrangement, and the rotation center of the reflector 8 is optimized, so that the wavelength without the mode hop in the optical gain wavelength range of the optical amplifier 1 is obtained. Variable is possible.

  FIG. 10 is a block diagram showing another example of the conventional external resonator type wavelength tunable light source described in “Patent Document 4”.

  In FIG. 10, 12 is an optical amplifier using a semiconductor laser having a non-reflective film on one emitting end, 13, 15, 17 and 22 are lenses, and 14 and 21 are light beams that pass light only in a predetermined direction. Isolators, 16 and 23 are optical fibers, 18 is a beam splitter, 19 is a diffraction grating as a wavelength selection element, and 20 is a reflector such as a mirror.

  The outgoing light from one outgoing end of the optical amplifier 12 becomes parallel light by the lens 13 and passes through the optical isolator 14. The light transmitted through the optical isolator 14 is collected by the lens 15 and enters one end of the optical fiber 16.

  The light emitted from the other light emitting end of the optical amplifier 12 is converted into parallel light by the lens 17 and is incident on the beam splitter 18, and the light transmitted through the beam splitter 18 is incident on the diffraction grating 19.

  The diffracted light from the diffraction grating 19 is incident on the reflector 20, and the reflected light from the reflector 20 is reflected by the diffraction grating 19 and is incident on the beam splitter 18 again.

  The light reflected by the beam splitter 18 enters the optical isolator 21, and the light transmitted through the optical isolator 21 is collected by the lens 22 and enters one end of the optical fiber 23. On the other hand, the light transmitted through the beam splitter 18 is collected by the lens 17 and is incident again on the other output end of the optical amplifier 12.

  Here, the operation of the conventional example shown in FIG. 10 will be described. The optical amplifier 12 is constituted by a semiconductor laser, and a non-reflective film is applied to one emission end indicated by “NR11” in FIG. 10, so that a driving current supplied from an optical amplifier driving means (not shown) is used. Accordingly, light in a wavelength region corresponding to the band gap energy of the active layer is emitted from the emission ends at both ends.

  The light emitted from one of the emission ends of the optical amplifier 12 to which the non-reflective film is applied enters the beam splitter 18 through the lens 11 and branches into reflected light and transmitted light depending on the branching ratio of the beam splitter 18. Is done.

  The light transmitted through the beam splitter 18 enters the diffraction grating 19 and reflects the parallel light to the reflector 20 at a diffraction angle corresponding to the wavelength of the incident light.

  Then, the reflected light from the reflector 20 is reflected by the diffraction grating 19 and enters the beam splitter 18 again. The light incident on the beam splitter 18 is branched into reflected light and transmitted light according to the branching ratio of the beam splitter 18.

  The light that has passed through the beam splitter 18 is collected by the lens 17 and is incident again on one output end of the optical amplifier 12.

  The light incident on the optical amplifier 12 from the diffraction grating 19 side propagates in the optical amplifier 12 and is reflected by the reflectance of the other emitting end not provided with the non-reflective film, propagates in the optical amplifier 12 and again becomes non-reflective. The light is emitted from the one emission end provided with the reflective film.

  Therefore, the light that does not pass through the other output end of the optical amplifier 12 that is not provided with the non-reflective film is configured between the reflector 20 and the other output end of the optical amplifier 12 that is not provided with the non-reflective film. The laser is oscillated by resonating with the resonator.

  On the other hand, the light transmitted through the other emitting end of the optical amplifier 1 that is not provided with the non-reflective film is incident on the optical fiber 5 through the lens 2, the optical isolator 3, and the lens 4 as laser light and used for various measurements. It is done.

  The light reflected by the diffraction grating 19 and reflected by the beam splitter 18 enters the optical fiber 23 through the optical isolator 21 and the lens 22 as laser light and is used for various measurements.

  In such a state, when the wavelength control means (not shown) changes the angle of the reflector 20 around the rotation center, the diffraction angle of the diffracted light reflected from the diffraction grating 19 perpendicularly incident on the reflector 20 is changed. Since it changes, the wavelength of laser oscillation changes. Further, since the resonator length of the resonator formed between the reflector 20 and the other emitting end of the optical amplifier 1 where the non-reflective film is not applied changes, the resonance wavelength also changes.

  As a result, the output light from one output end of the optical amplifier 12 on which the non-reflective film is applied is incident on the diffraction grating 19, and the diffracted light of the diffraction grating 19 is reflected again on the diffraction grating 19 by the reflector 20. The light returned from the diffraction grating 19 is disposed so as to be incident on one emission end of the optical amplifier 12 on which the non-reflective film is applied, and the reflector 20 and the other on which the optical amplifier 12 is not provided with the non-reflective film. By forming a resonator with the emission end and changing the angle of the reflector 20, the wavelength of laser oscillation can be changed.

  Further, since the laser light incident on the optical fiber 23 is light whose wavelength is selected by the diffraction grating 19 and the reflector 20, a laser with a low ASE light level from which spontaneous emission light (ASE (Amplified Spountaneous Emission) light) is removed. Become light.

  However, in the conventional example shown in FIGS. 9 and 10, the optical gain wavelength range of the optical amplifier is determined by the composition of the optical amplifier, and the semiconductor laser used as the optical amplifier can obtain a laser oscillation wavelength range of about “200 nm”. However, there is a problem that the usable wavelength range in which practical light intensity can be obtained is about “150 nm”.

  Further, the conventional example shown in FIGS. 9 and 10 has a problem that it is difficult to reduce the size because a discrete optical component is used as the diffraction grating and reflector, or the diffraction grating, reflector and beam splitter. there were.

Furthermore, the conventional example shown in FIG. 10 has a problem that there are many optical axis adjustment portions of the optical components, and it becomes difficult to adjust the optical axes of the optical components.
Accordingly, the problem to be solved by the present invention is to realize an external resonator type wavelength tunable light source that expands the wavelength tunable range, is easy to adjust the optical axis, and can be miniaturized.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
The first and second optical amplifiers having different reflection wavelength ranges with one non-reflective film on one output end, and the output from one output end on which the non-reflective film of these first and second optical amplifiers is applied. First and second optical waveguides into which incident light is incident, a third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region, and the third A lens that makes the outgoing light from one outgoing end of the optical waveguide provided with the non-reflective film parallel light, and the outgoing light from this lens is incident and the reflected light is passed through the lens to the third Wavelength selective reflection means for entering one output end of the optical waveguide provided with the non-reflective film, and light emitted from the other output end provided with the non-reflective film of the third optical waveguide enter one end. With an optical fiber that outputs outgoing light from the other end. It is possible to expand a wavelength variable range of laser oscillation enables utilization of light emitted respectively different two optical amplifiers Re.

The invention according to claim 2
In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
The first and second optical amplifiers having different reflection wavelength ranges with one non-reflective film on one output end, and the output from one output end on which the non-reflective film of these first and second optical amplifiers is applied. First and second optical waveguides into which incident light is incident, a third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region, and the third A first lens that converts the outgoing light from one outgoing end of the optical waveguide provided with the non-reflective film into parallel light, and the outgoing light from the first lens is incident and the reflected light is converted into the first light. A wavelength selective reflection means for entering one of the output ends of the third optical waveguide provided with the non-reflective film through the lens; and the other output end of the third optical waveguide provided with the non-reflective film A second lens that converts the emitted light from the light into parallel light, and the parallel light from the second lens is incident An optical isolator, a third lens that collects light emitted from the optical isolator, and an optical fiber that emits light emitted from the third lens at one end and outputs light from the other end. Since the light emitted from two optical amplifiers having different wavelength ranges can be used, the wavelength variable range for laser oscillation can be expanded.

The invention described in claim 3
In the external resonator type wavelength tunable light source which is the invention according to claim 1 or claim 2,
The wavelength selective reflection means is
A reflector having a variable angle around the rotation center, and the incident parallel light is emitted to the reflector as diffracted light, and the reflected light from the reflector is transmitted through the lens or the first lens. The wavelength of the laser oscillation because the light emitted from the two optical amplifiers having different wavelength ranges can be used by comprising the diffraction grating that is incident on one of the output ends of the third optical waveguide provided with the non-reflective film. The variable range can be expanded. Further, since the laser light incident on the optical fiber is light whose wavelength is selected by the diffraction grating and the reflector, it becomes a laser light with a low ASE light level from which spontaneous emission light (ASE light) is removed. The optical arrangement of the optical amplifier 1, the diffraction grating 7, and the reflector 8 is changed to a Littman arrangement, and the rotation center of the reflector 8 is optimized, so that wavelength tunability without mode hops can be achieved in the optical gain wavelength range of the optical amplifier 1. It becomes possible.

The invention according to claim 4
In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
The first and second optical amplifiers having different reflection wavelength ranges with one non-reflective film on one output end, and the output from one output end on which the non-reflective film of these first and second optical amplifiers is applied. First and second optical waveguides into which incident light is incident, a third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region, and the third Wavelength selective reflection means for allowing outgoing light from one outgoing end of the optical waveguide to be incident and reflecting light to one outgoing end of the third optical waveguide; and a non-reflective film of the third optical waveguide Since the output light from the other output end to which the light is applied is input to one end and the output light is output from the other end, the output light of two optical amplifiers having different wavelength ranges can be used. The wavelength variable range for laser oscillation can be expanded. That.

The invention according to claim 5
In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
The first and second optical amplifiers having different reflection wavelength ranges with one non-reflective film on one output end, and the output from one output end on which the non-reflective film of these first and second optical amplifiers is applied. First and second optical waveguides into which incident light is incident, a third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region, and the third Wavelength selective reflection means for allowing outgoing light from one outgoing end of the optical waveguide to be incident and reflecting light to one outgoing end of the third optical waveguide; and a non-reflective film of the third optical waveguide The first lens that makes the outgoing light from the other outgoing end subjected to the parallel light, the optical isolator to which the parallel light from the first lens is incident, and the outgoing light of this optical isolator is condensed The second lens and the light emitted from this second lens is incident on one end By providing an optical fiber for outputting the light emitted from, it is possible to expand a wavelength variable range of laser oscillation enables utilization of light emitted different two optical amplifiers in the wavelength range.

The invention described in claim 6
In the external resonator type wavelength tunable light source according to claim 4 or claim 5,
The wavelength selective reflection means is
A waveguide type lens formed in a slab optical waveguide that converts light emitted from the third optical waveguide into plane-parallel light, a reflector whose angle is variable around the rotation center, and the waveguide type lens. A diffraction grating formed in a slab optical waveguide that emits the plane parallel light as diffracted light to the reflector and makes the reflected light from the reflector enter the third optical waveguide via the waveguide lens. Since the light emitted from the two optical amplifiers having different wavelength ranges can be used, the wavelength variable range for laser oscillation can be expanded. Further, since the laser light incident on the optical fiber is light that has been wavelength-selected by the diffraction grating region and the reflector, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed. Further, since the lenses and diffraction gratings of discrete optical components other than the reflector are not used, the optical axis can be easily adjusted, and the optical system can be downsized.

The invention described in claim 7
In the external resonator type wavelength tunable light source according to claim 4 or claim 5,
The wavelength selective reflection means is
A reflector having a variable angle around the center of rotation, and light emitted from the third optical waveguide is converted into plane-parallel light, and the plane-parallel light is emitted as diffracted light to the reflector. Since it is composed of the diffraction grating region formed in the slab optical waveguide that collects the reflected light and enters the third optical waveguide, the light emitted from two optical amplifiers having different wavelength ranges can be used. It is possible to expand the wavelength variable range for laser oscillation. Further, since the laser light incident on the optical fiber is light that has been wavelength-selected by the diffraction grating region and the reflector, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed. Further, since the function of the waveguide lens is also provided in the diffraction grating region, the optical system can be further downsized.

The invention described in claim 8
In the external resonator type wavelength tunable light source according to any one of claims 1 to 3,
The third optical waveguide formed on the optical substrate and the third optical waveguide formed on the optical substrate in parallel on both sides of the third optical waveguide, and the intermediate portions are close to the third optical waveguide, respectively. By providing the first and second optical waveguides constituting the demultiplexing / multiplexing region, it is possible to use the light emitted from two optical amplifiers having different wavelength ranges, thereby expanding the wavelength variable range for laser oscillation. It becomes possible to do. Further, since the laser light incident on the optical fiber is light whose wavelength is selected by the diffraction grating and the reflector, it becomes a laser light with a low ASE light level from which spontaneous emission light (ASE light) is removed. The optical arrangement of the optical amplifier 1, the diffraction grating 7, and the reflector 8 is changed to a Littman arrangement, and the rotation center of the reflector 8 is optimized, so that wavelength tunability without mode hops can be achieved in the optical gain wavelength range of the optical amplifier 1. It becomes possible.

The invention according to claim 9
In the external resonator type wavelength tunable light source according to claim 6,
The third optical waveguide formed on the optical substrate and the third optical waveguide formed on the optical substrate in parallel on both sides of the third optical waveguide, and the intermediate portions are close to the third optical waveguide, respectively. The first and second optical waveguides constituting the demultiplexing / multiplexing region, and the waveguide type lens and the diffraction grating region formed on the optical substrate and in the slab optical waveguide. Thus, the light emitted from two optical amplifiers having different wavelength ranges can be used, so that the wavelength variable range for laser oscillation can be expanded. Further, since the laser light incident on the optical fiber is light that has been wavelength-selected by the diffraction grating region and the reflector, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed. Further, since the lenses and diffraction gratings of discrete optical components other than the reflector are not used, the optical axis can be easily adjusted, and the optical system can be downsized.

The invention according to claim 10 is:
In the external resonator type wavelength tunable light source according to claim 7,
The third optical waveguide formed on the optical substrate and the third optical waveguide formed on the optical substrate in parallel on both sides of the third optical waveguide, and the intermediate portions are close to the third optical waveguide, respectively. Each of the wavelength ranges by providing the first and second optical waveguides constituting the demultiplexing / multiplexing region and the diffraction grating region formed on the optical substrate and in the slab optical waveguide. Since the light emitted from two different optical amplifiers can be used, the wavelength variable range for laser oscillation can be expanded. Further, since the laser light incident on the optical fiber is light that has been wavelength-selected by the diffraction grating region and the reflector, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed. Further, since the function of the waveguide lens is also provided in the diffraction grating region, the optical system can be further downsized.

The invention according to claim 11
In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
The first and second optical amplifiers having different reflection wavelength ranges with one non-reflective film on one output end, and the output from one output end on which the non-reflective film of these first and second optical amplifiers is applied. First and second optical waveguides into which incident light is incident, respectively, and a high-reflection film is provided at one end where light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region 3, a surface acoustic wave type wavelength filter provided between one output end provided with the highly reflective film of the third optical waveguide and the demultiplexing / multiplexing region, the third optical waveguide, High-speed wavelength tuning is possible over a wide wavelength range by providing an optical fiber that emits light from the other output end with an anti-reflection film on the optical waveguide and enters the output from the other end. Because there is no light emitted to the optical substrate, optical axis adjustment is almost unnecessary. It will be.

The present invention has the following effects.
According to the first, second, fourth and fifth aspects of the present invention, the first and second light beams emitted from one of the light emitting ends on which the non-reflective films of the two optical amplifiers having different wavelength ranges are applied. Light incident on the optical waveguide and coupled to the third optical waveguide in the demultiplexing / multiplexing region is incident on the wavelength selective reflection means, and the reflected light from the wavelength selective reflection means is incident on the third optical waveguide again to separate the light. The light coupled to the first or second optical waveguide in the wave combining region is incident on the two optical amplifiers, and between the reflector and the other output end of the two optical amplifiers where the non-reflective film is not applied. By configuring the resonator and changing the angle of the reflector, the light emitted from two optical amplifiers having different wavelength ranges can be used, so that the variable wavelength range for laser oscillation can be expanded.

  According to the third and eighth aspects of the present invention, since the laser light incident on the optical fiber is light whose wavelength is selected by the diffraction grating and the reflector, the spontaneous emission light (ASE light) is removed. The laser light becomes an ASE light level. The optical arrangement of the optical amplifier 1, the diffraction grating 7, and the reflector 8 is changed to a Littman arrangement, and the rotation center of the reflector 8 is optimized, so that wavelength tunability without mode hops can be achieved in the optical gain wavelength range of the optical amplifier 1. It becomes possible.

  According to the invention of claim 6 and claim 9, the waveguide type lens formed in the slab optical waveguide that makes the outgoing light from one outgoing end of the third optical waveguide parallel light, and the rotation center A reflector having a variable angle at the center and parallel light incident from the waveguide lens are emitted as diffracted light to the reflector, and the reflected light from the reflector passes through the waveguide lens to the third optical waveguide. By constructing the wavelength selective reflection means from the diffraction grating region formed in the incident slab optical waveguide, the light emitted from two optical amplifiers having different wavelength ranges can be used, so that the wavelength variable range for laser oscillation can be expanded. Is possible. Further, since the laser light incident on the optical fiber is light that has been wavelength-selected by the diffraction grating region and the reflector, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed. Further, since the lenses and diffraction gratings of discrete optical components other than the reflector are not used, the optical axis can be easily adjusted, and the optical system can be downsized.

  According to the seventh and tenth aspects of the present invention, the reflector having a variable angle around the rotation center and the light emitted from one of the light emitting ends of the third optical waveguide are converted into parallel light and parallel light. The wavelength selective reflection means is composed of a diffraction grating region formed in the slab optical waveguide that emits the light as diffracted light to the reflector, collects the reflected light from the reflector, and enters the third optical waveguide. Since the light emitted from two optical amplifiers having different wavelength ranges can be used, the wavelength variable range for laser oscillation can be expanded. Further, since the laser light incident on the optical fiber is light that has been wavelength-selected by the diffraction grating region and the reflector, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed. Further, since the function of the waveguide lens is also provided in the diffraction grating region, the optical system can be further downsized.

  According to the eleventh aspect of the present invention, the high reflection film is formed on the other end of the third optical waveguide, and is formed between the high reflection film and the demultiplexing / multiplexing region on the third optical waveguide. By providing the surface acoustic wave type wavelength filter, it becomes possible to change the wavelength at high speed in a wide wavelength range, and since there is no light emitted to the optical substrate, optical axis adjustment becomes almost unnecessary.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an external resonator type wavelength tunable light source according to the present invention.

  In FIG. 1, reference numeral 24 denotes an optical substrate on which three optical waveguides having a demultiplexing / multiplexing region are formed using a quartz-based material, an organic material, or a semiconductor material, and 25 is formed on the optical substrate 24 and is not provided at one emission end. An optical amplifier using a semiconductor laser provided with a reflective film, 26 is an optical amplifier using a semiconductor laser formed on the optical substrate 24 and provided with a non-reflective film at one emission end and having a wavelength range different from that of the optical amplifier 25. 27, 29, and 31 are lenses, 28 is an optical isolator that allows light to pass only in a predetermined direction, 30 is an optical fiber, 32 is a diffraction grating that is a wavelength selection element, and 33 is a reflector such as a mirror. Reference numerals 32 and 33 constitute wavelength selective reflection means 52.

  FIG. 2 is an explanatory diagram (plan view) for explaining the details of the optical substrate 24. In FIG. 2, 24, 25, 26, NR21 and NR22 are assigned the same reference numerals as in FIG. 1, 34, 35 and 36 are optical waveguides formed on the optical substrate 24, and 37 is light coupled with a certain coupling efficiency. This is a demultiplexing / multiplexing region.

  In FIG. 2, a linear optical waveguide 36 is formed on the optical substrate 24, and an optical waveguide 34 and an optical waveguide 35 are formed in parallel on both sides of the optical waveguide 36, and an intermediate portion between the optical waveguide 34 and the optical waveguide 35. Respectively constitute a demultiplexing / multiplexing region 37 in the vicinity of the optical waveguide 36.

  As shown by “NR21” in FIG. 2, a non-reflective film is applied to one end of the optical waveguide 34, the optical waveguide 35 and the optical waveguide 36, and also to the other end of the optical waveguide 36 as shown by “NR22” in FIG. An antireflective film is applied. One end of the optical amplifier 25 and the optical amplifier 26 is connected to the other ends of the optical waveguide 34 and the optical waveguide 35.

  Further, in the optical amplifier 25 and the optical amplifier 26, a non-reflective film is applied to one emission end indicated by “NR31” and “NR32” in FIG.

  On the other hand, in FIG. 1, the light emitted from one end of the optical waveguide 36 provided with the antireflection film indicated by “NR22” in FIG. 1 is converted into parallel light by the lens 27 and is transmitted through the optical isolator 28. The light transmitted through the optical isolator 28 is collected by the lens 29 and is incident on one end of the optical fiber 30.

  Light emitted from the other end of the optical waveguide 36 provided with the non-reflective film indicated by “NR 21” in FIG. 1 is converted into parallel light by the lens 31 and is incident on the diffraction grating 32. The diffracted light from the diffraction grating 32 is incident on the reflector 33. Of the diffracted light incident on the reflector 33, the diffracted light from the diffraction grating perpendicularly incident on the reflector 33 becomes vertical reflected light from the reflector 33 and is diffracted by the diffraction grating 32 and collected by the lens 31. Then, the light is again incident on the other end of the optical waveguide 36 to which the antireflection film is applied. Diffracted light from the diffraction grating that is not perpendicularly incident on the reflector 33 is reflected at different angles, so that even if it is diffracted by the diffraction grating 32 and collected by the lens 31, other than the optical waveguide 36 on which a non-reflective film is applied. Not incident on the edge.

  Here, the operation of the embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 3 is a characteristic curve diagram showing the relationship between the oscillation wavelength range of the optical amplifier 25 and the optical amplifier 26 and the coupling efficiency of the demultiplexing / multiplexing region 37.

  The optical amplifier 25 and the optical amplifier 26 are constituted by semiconductor lasers, and emit light from a wavelength region corresponding to the band gap energy of the active layer from both emission ends in accordance with the supplied drive current. However, the oscillation wavelength ranges of the optical amplifier 25 and the optical amplifier 26 have different oscillation wavelength ranges as indicated by “WR41” and “WR42” in FIG.

  The coupling efficiency between the optical waveguide 34 and the optical waveguide 36 has a coupling efficiency of about 80% within the oscillation wavelength range “WR41” of the optical amplifier 25, and within the oscillation wavelength range “WR42” of the optical amplifier 26. Is a characteristic that is rapidly decreasing.

  As a result, the light from the optical amplifier 25 which has propagated through the optical waveguide 34 and reached the demultiplexing / multiplexing region 37 enters the optical waveguide 36 with a coupling efficiency of about 80% as shown by “CH41” in FIG. The light is coupled and propagates through the optical waveguide 36.

  On the other hand, the coupling efficiency between the optical waveguide 35 and the optical waveguide 36 has a coupling efficiency of about 80% within the oscillation wavelength range “WR42” of the optical amplifier 26, and within the oscillation wavelength range “WR41” of the optical amplifier 25. This is a characteristic in which the coupling efficiency is rapidly reduced.

  As a result, the light from the optical amplifier 26 that has propagated through the optical waveguide 35 and reached the demultiplexing / multiplexing region 37 enters the optical waveguide 36 with a coupling efficiency of about 80% as shown by “CH42” in FIG. The light is coupled and propagates through the optical waveguide 36.

  The light emitted from the optical amplifier 25 and the optical amplifier 26 propagating through the optical waveguide 36 in this way is emitted from the other end of the optical waveguide 36 on which the antireflection film indicated by “NR21” in FIG. It becomes light and enters the wavelength selective reflection means 52, in other words, enters the diffraction grating 32 constituting the wavelength selective reflection means 52.

  The diffracted light from the diffraction grating 32 is incident on the reflector 33. Of the diffracted light incident on the reflector 33, the diffracted light from the diffraction grating perpendicularly incident on the reflector 33 becomes vertical reflected light from the reflector 33 and is diffracted by the diffraction grating 32 and collected by the lens 31. Then, the light is again incident on the other end of the optical waveguide 36 to which the antireflection film is applied. Diffracted light from the diffraction grating that is not perpendicularly incident on the reflector 33 is reflected at different angles, so that even if it is diffracted by the diffraction grating 32 and collected by the lens 31, other than the optical waveguide 36 on which a non-reflective film is applied. Not incident on the edge.

  The reflected light from the reflection selecting means 52 is collected by the lens 31 and is incident again on the other end of the optical waveguide 36 to which the non-reflective film indicated by “NR21” in FIG.

  Of the reflected light from the reflection selection means that propagates through the optical waveguide 36 and reaches the demultiplexing / multiplexing region 37, the light in the wavelength range WR41 is coupled by about 80% as shown by “CH41” in FIG. It is coupled to the optical waveguide 34 with efficiency and enters the optical amplifier 25. On the other hand, since the coupling efficiency to the optical waveguide 35 is reduced, the amount of light propagating through the optical waveguide 35 and entering the optical amplifier 26 is very small.

  Similarly, of the reflected light from the reflection selection means that propagates through the optical waveguide 36 and reaches the demultiplexing / multiplexing region 37, the light in the wavelength range WR42 is about 80% as shown by "CH42" in FIG. Are coupled to the optical waveguide 35 with a coupling efficiency of On the other hand, since the coupling efficiency to the optical waveguide 34 is reduced, the amount of light that propagates through the optical waveguide 34 and enters the optical amplifier 25 is very small.

  The light that has entered the optical amplifier 25 or 26 from the optical waveguide 36 propagates through the optical amplifier 25 or 26 and is reflected at the reflectance of the other exit end that is not provided with the nonreflective film. Alternatively, the light is propagated through the optical amplifier 26 and is emitted from one emission end where the antireflection film is applied again.

  For this reason, the light that does not pass through the other emission end of the optical amplifier 25 or 26 that is not provided with the non-reflective film is the other of the reflector 33 and the optical amplifier 25 or the optical amplifier 26 that is not provided with the non-reflective film. The laser is oscillated by resonating with a resonator formed between the light emitting end of the first and second light emitting ends.

  On the other hand, the light which has propagated through the optical waveguide 36 and has not been coupled to the optical waveguide 34 or the optical waveguide 35 in the demultiplexing / multiplexing region 37 propagates through the optical waveguide 36 as it is and is a non-reflective film indicated by “NR22” in FIG. The light is emitted from the other end of the optical waveguide 36 to which is applied.

  As described above, the light emitted from the other end of the optical waveguide 36, the lens 27, the optical isolator 28, and the lens 29 are incident on the optical fiber 30 and used for various measurements.

  In this state, when the wavelength control means (not shown) changes the angle of the reflector 33 around the rotation center, the diffraction angle of the diffracted light reflected from the diffraction grating 32 perpendicularly incident on the reflector 33 is changed. Since it changes, the wavelength of laser oscillation changes. Further, since the resonator length of the resonator formed between the reflector 33 and the other emitting end of the optical amplifier 26 on which the non-reflective film is not applied changes, the resonance wavelength also changes.

  As a result, the light emitted from one of the light emitting ends of the optical amplifier 25 and the optical amplifier 26 on which the non-reflective film is applied enters the optical waveguide 34 and the optical waveguide 35, and enters the optical waveguide 36 in the demultiplexing / multiplexing region 37. The combined light is incident on the wavelength selective reflection means 52, the reflected light from the wavelength selective reflection means 52 is incident on the optical waveguide 36 again, and the light coupled to the optical waveguide 34 or the optical waveguide 35 in the demultiplexing / multiplexing region 37. A resonator is formed between the reflector 33 and the other output end of the optical amplifier 25 and the optical amplifier 26 on which the non-reflective film is not applied, and the angle of the reflector 33. By changing, the light emitted from two optical amplifiers having different wavelength ranges can be used, so that the wavelength variable range for laser oscillation can be expanded.

  Further, since the laser light incident on the optical fiber 30 is light whose wavelength is selected by the diffraction grating 32 and the reflector 33, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed.

  In addition, the optical arrangement of the optical amplifier 1, the diffraction grating 7, and the reflector 8 is set to the Littman arrangement, and the rotation center of the reflector 8 is optimized, so that the wavelength without the mode hop in the optical gain wavelength range of the optical amplifier 1 is obtained. Variable is possible.

  FIG. 4 is a block diagram showing another embodiment of the external resonator type wavelength tunable light source according to the present invention.

  In FIG. 4, 27, 28, 29 and 30 are assigned the same reference numerals as in FIG. 1, and 38 is formed of three optical waveguides having a demultiplexing / multiplexing region using a quartz-based material, an organic material or a semiconductor material. The optical substrate 39 is an optical amplifier using a semiconductor laser formed on the optical substrate 38 and is provided with a non-reflective film on one output end, and 40 is an anti-reflective film formed on the optical substrate 38 on one output end. The optical amplifier 39 is an optical amplifier using a semiconductor laser having a different wavelength range.

  5 and 6 are explanatory views (plan view and side view) for explaining details of the optical substrate 38. FIG. 5 and 6, 38, 39, 40 and NR51 are given the same reference numerals as in FIG. 4, 41, 42 and 43 are optical waveguides formed on the optical substrate 38, 44 is light with a certain coupling efficiency. Demultiplexing / multiplexing region 45 to be coupled, 45 is a waveguide type lens formed in the slab optical waveguide (planar optical waveguide), 46 is a diffraction grating region formed in the slab optical waveguide (planar optical waveguide), and 47 is a mirror. Etc. is a reflector. Reference numerals 46 and 47 constitute wavelength selective reflection means 53.

  In FIG. 5, a linear optical waveguide 43 is formed on the optical substrate 38, and an optical waveguide 41 and an optical waveguide 42 are formed in parallel on both sides of the optical waveguide 43, and an intermediate portion between the optical waveguide 41 and the optical waveguide 42 is A demultiplexing / multiplexing region 44 is formed in the vicinity of each of the optical waveguides 43.

  As shown by “NR51” in FIG. 5, a non-reflective film is applied to one end of the optical waveguide 43, and one output end of the optical amplifier 39 and the optical amplifier 40 is connected to one end of the optical waveguide 41 and the optical waveguide. Formed as follows.

  Further, in the optical amplifier 39 and the optical amplifier 40, a non-reflective film is applied to one emission end indicated by “NR61” and “NR62” in FIG.

  On the other hand, in FIG. 4, the light emitted from one end of the optical waveguide 43 provided with the antireflection film indicated by “NR51” in FIG. 4 is converted into parallel light by the lens 27 and is transmitted through the optical isolator 28. The light transmitted through the optical isolator 28 is collected by the lens 29 and is incident on one end of the optical fiber 30.

  Light emitted from the other end of the optical waveguide 43 propagates through a slab optical waveguide (planar optical waveguide) formed on the optical substrate 38, and is parallel in a plane by a waveguide lens 45 formed in the slab optical waveguide (planar optical waveguide). It becomes light and enters the diffraction grating region 46 formed in the slab optical waveguide (planar optical waveguide).

  In the diffraction grating region 46, incident light is emitted from the slab optical waveguide (planar optical waveguide) to the outside of the optical substrate 38 at an angle corresponding to the wavelength, and the emitted light is incident on a reflector 47 disposed outside the optical substrate 38. The

  Of the diffracted light incident on the reflector 47, the diffracted light from the diffraction grating region perpendicularly incident on the reflector 47 becomes the vertical reflected light of the reflector 47 and is diffracted by the diffraction grating region 46 and is of the waveguide type. The light is condensed by the lens 45 and is incident on the other end of the optical waveguide 43 again. Diffracted light from the diffraction grating region that is not perpendicularly incident on the reflector 47 is reflected at different angles, so that even if it is diffracted by the diffraction grating region 46 and collected by the waveguide lens 45, it is reflected at the other end of the optical waveguide 43. Not incident.

  Here, the operation of another embodiment shown in FIG. 4 will be described with reference to FIG. In FIG. 3, the characteristic curve diagram showing the relationship between the oscillation wavelength range of each of the optical amplifiers 39 and 40 and the coupling efficiency of the demultiplexing / multiplexing region 44 is used as a replacement.

  The optical amplifier 39 and the optical amplifier 40 are constituted by semiconductor lasers, and emit light in a wavelength region corresponding to the band gap energy of the active layer from both emission ends in accordance with the supplied drive current. However, the oscillation wavelength ranges of the optical amplifier 39 and the optical amplifier 40 are assumed to have different oscillation wavelength ranges as indicated by “WR41” and “WR42” in FIG.

  The coupling efficiency between the optical waveguide 41 and the optical waveguide 43 has a coupling efficiency of about 80% within the oscillation wavelength range “WR41” of the optical amplifier 39, and within the oscillation wavelength range “WR42” of the optical amplifier 40. Is a characteristic that is rapidly decreasing.

  As a result, the light from the optical amplifier 39 that has propagated through the optical waveguide 39 and reached the demultiplexing / multiplexing region 44 enters the optical waveguide 43 with a coupling efficiency of about 80%, as shown by “CH41” in FIG. The light is coupled and propagates through the optical waveguide 43.

  On the other hand, the coupling efficiency between the optical waveguide 42 and the optical waveguide 43 has a coupling efficiency of about 80% within the oscillation wavelength range “WR42” of the optical amplifier 40, and within the oscillation wavelength range “WR41” of the optical amplifier 39. This is a characteristic in which the coupling efficiency is rapidly reduced.

  As a result, the light from the optical amplifier 40 that has propagated through the optical waveguide 42 and reached the demultiplexing / multiplexing region 44 enters the optical waveguide 43 with a coupling efficiency of about 80%, as indicated by “CH42” in FIG. The light is coupled and propagates through the optical waveguide 43.

  Thus, the light emitted from the optical amplifier 39 and the optical amplifier 40 propagating through the optical waveguide 43 is emitted from one end of the optical waveguide 43, converted into plane parallel light by the waveguide lens 45, and is incident on the diffraction grating region 46.

  The diffracted light in the diffraction grating region 46 is incident on the reflector 47, and the diffracted light in the diffraction grating region 46 is incident on the reflector 47. Of the diffracted light incident on the reflector 47, the diffracted light from the diffraction grating perpendicularly incident on the reflector 47 becomes vertical reflected light from the reflector 47, and is diffracted by the diffraction grating region 46 to be a waveguide lens. The light is condensed by 45 and incident on the other end of the optical waveguide 43 again. Diffracted light from the diffraction grating that is not perpendicularly incident on the reflector 47 is reflected at different angles, so that it is incident on the other end of the optical waveguide 43 even if it is diffracted by the diffraction grating region 46 and condensed by the waveguide lens 45. Not.

  The reflected light from the reflection selecting means 53 is collected by the waveguide lens 45 and is incident on the other end of the optical waveguide 43 again.

  Of the reflected light from the reflection selection means that propagates through the optical waveguide 43 and reaches the demultiplexing / multiplexing region 44, the light in the wavelength range “WR41” is about 80% as shown by “CH41” in FIG. Is coupled to the optical waveguide 41 with a coupling efficiency of On the other hand, since the coupling efficiency to the optical waveguide 42 is reduced, the amount of light that propagates through the optical waveguide 42 and enters the optical amplifier 40 is very small.

  Similarly, the light in the wavelength range “WR42” among the reflected light from the reflection selection means that propagates through the optical waveguide 43 and reaches the demultiplexing / multiplexing region 44 is 80 as shown by “CH42” in FIG. It is coupled to the optical waveguide 42 with a coupling efficiency of about% and enters the optical amplifier 40. On the other hand, since the coupling efficiency to the optical waveguide 41 is reduced, the amount of light that propagates through the optical waveguide 41 and enters the optical amplifier 39 is very small.

  The light that has entered the optical amplifier 39 or the optical amplifier 40 from the optical waveguide 43 propagates through the optical amplifier 39 or the optical amplifier 40 and is reflected at the reflectance of the other emitting end that is not provided with the non-reflective film. Alternatively, the light is propagated through the optical amplifier 40 and is emitted from one emission end where the antireflection film is applied again.

  For this reason, the light that does not pass through the other output end of the optical amplifier 39 or the optical amplifier 40 that is not provided with the non-reflective film is not reflected by the reflector 47 and the other of the optical amplifier 39 or the optical amplifier 40 that is not provided with the non-reflective film. The laser is oscillated by resonating with a resonator formed between the light emitting end of the first and second light emitting ends.

  On the other hand, the light that has propagated through the optical waveguide 43 and has not been coupled to the optical waveguide 41 or the optical waveguide 42 in the demultiplexing / multiplexing region 44 propagates through the optical waveguide 43 as it is and is a non-reflective film indicated by “NR51” in FIG. The light is emitted from the other end of the optical waveguide 43 to which is applied.

  Thus, the light emitted from the other end of the optical waveguide 43 enters the optical fiber 30 via the lens 27, the optical isolator 28, and the lens 29, and is used for various measurements.

  In this state, when the wavelength control means changes the angle of the reflector 47 as shown by “RT71” in FIG. 6 around the rotation center as shown by “RC71” in FIG. Since the diffraction angle of the diffracted light emitted from the incident diffraction grating region 46 changes, the laser oscillation wavelength changes. Further, since the resonator length of the resonator formed between the reflector 47 and the other emitting end of the optical amplifier 40 on which the non-reflective film is not applied changes, the resonance wavelength also changes.

  As a result, the outgoing light from one of the outgoing ends of the optical amplifier 39 and the optical amplifier 40 on which the non-reflective film is applied enters the optical waveguide 41 and the optical waveguide 42, and enters the optical waveguide 43 in the demultiplexing / multiplexing region 44. The combined light is incident on the wavelength selective reflection means 53, the reflected light from the wavelength selective reflection means 53 is incident on the optical waveguide 43 again, and the light coupled to the optical waveguide 41 or the optical waveguide 42 in the demultiplexing / multiplexing region 44. A light is incident on the optical amplifier 39 or the optical amplifier 40 to form a resonator between the reflector 47 and the other output end of the optical amplifier 39 and the optical amplifier 40 on which the non-reflective film is not applied, and the angle of the reflector 47. By changing, the light emitted from two optical amplifiers having different wavelength ranges can be used, so that the wavelength variable range for laser oscillation can be expanded.

  Further, since the laser light incident on the optical fiber 30 is light whose wavelength is selected by the diffraction grating region 46 and the reflector 47, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed.

  Further, compared to the embodiment shown in FIG. 1, since the lens 31 and the diffraction grating 32 of the discrete optical components other than the reflector 47 are not used, the optical axis can be easily adjusted and the optical system can be downsized. .

  FIG. 7 is a configuration block diagram showing another embodiment of the external resonator type wavelength tunable light source according to the present invention.

  7, reference numerals 27, 28, 29, 30, 39 and 40 are assigned the same reference numerals as in FIG. 4, and reference numeral 38a denotes three light beams having a demultiplexing / multiplexing region using a quartz material, an organic material or a semiconductor material. An optical substrate on which a waveguide is formed.

  FIG. 8 is an explanatory view (plan view) for explaining details of the optical substrate 38a. However, the positional relationship of the reflectors is the same as the explanatory diagram (side view) shown in FIG.

  8, 38a, 39, 40 and NR81 have the same reference numerals as in FIG. 7, 41, 42, 43, 44, NR61 and NR62 have the same reference numerals as in FIG. 5, and 47 has the same reference numerals as in FIG. , 48 is a diffraction grating region having a waveguide type lens function formed in a slab optical waveguide (planar optical waveguide). Reference numerals 47 and 48 constitute wavelength selective reflection means 54 (not shown).

  In FIG. 8, a linear optical waveguide 43 is formed on the optical substrate 38a, and an optical waveguide 41 and an optical waveguide 42 are formed in parallel on both sides of the optical waveguide 43, and an intermediate portion between the optical waveguide 41 and the optical waveguide 42 is A demultiplexing / multiplexing region 44 is formed in the vicinity of each of the optical waveguides 43.

  As shown by “NR81” in FIG. 8, a non-reflective film is applied to one end of the optical waveguide 43, and one output end of the optical amplifier 39 and the optical amplifier 40 is connected to one end of the optical waveguide 41 and the optical waveguide. Formed as follows.

  Further, in the optical amplifier 39 and the optical amplifier 40, a non-reflective film is applied to one emission end indicated by “NR61” and “NR62” in FIG.

  On the other hand, in FIG. 7, light emitted from one end of the optical waveguide 43 provided with the non-reflective film indicated by “NR81” in FIG. 7 is converted into parallel light by the lens 27 and is transmitted through the optical isolator 28. The light transmitted through the optical isolator 28 is collected by the lens 29 and is incident on one end of the optical fiber 30.

  The light emitted from the other end of the optical waveguide 43 propagates through the slab optical waveguide (planar optical waveguide) formed on the optical substrate 38a, and the waveguide type of the diffraction grating region 48 formed in the slab optical waveguide (planar optical waveguide). It becomes plane parallel light by the lens function.

  In the diffraction grating region 48, incident light is emitted from the slab optical waveguide (planar optical waveguide) to the outside of the optical substrate 38 a at an angle corresponding to the wavelength, and the emitted light is incident on a reflector 47 disposed outside the optical substrate 38. The

  Of the diffracted light incident on the reflector 47, the diffracted light from the diffraction grating perpendicularly incident on the reflector 47 becomes vertical reflected light from the reflector 47, and is diffracted by the diffraction grating region 48. The light is condensed by the waveguide type lens function and is incident on the other end of the optical waveguide 43 again. Diffracted light from the diffraction grating that does not enter the reflector 33 at a normal angle is reflected at different angles, so that even if it is diffracted by the diffraction grating 47 and condensed by the waveguide type lens function of the diffraction grating region 48, It is not incident on the other end.

  Here, the operation of another embodiment shown in FIG. 7 will be described with reference to FIG. In FIG. 3, the characteristic curve diagram showing the relationship between the oscillation wavelength range of the optical amplifier 39 and the optical amplifier 40 and the coupling efficiency of the demultiplexing / multiplexing region 44 is used as a replacement.

  The optical amplifier 39 and the optical amplifier 40 are constituted by semiconductor lasers, and emit light in a wavelength region corresponding to the band gap energy of the active layer from both emission ends in accordance with the supplied drive current. However, the oscillation wavelength ranges of the optical amplifier 39 and the optical amplifier 40 are assumed to have different oscillation wavelength ranges as indicated by “WR41” and “WR42” in FIG.

  The coupling efficiency between the optical waveguide 41 and the optical waveguide 43 has a coupling efficiency of about 80% within the oscillation wavelength range “WR41” of the optical amplifier 39, and within the oscillation wavelength range “WR42” of the optical amplifier 40. Is a characteristic that is rapidly decreasing.

  As a result, the light from the optical amplifier 39 that has propagated through the optical waveguide 41 and reached the demultiplexing / multiplexing region 44 enters the optical waveguide 43 with a coupling efficiency of about 80%, as shown by “CH41” in FIG. The light is coupled and propagates through the optical waveguide 43.

  On the other hand, the coupling efficiency between the optical waveguide 42 and the optical waveguide 43 has a coupling efficiency of about 80% within the oscillation wavelength range “WR42” of the optical amplifier 40, and within the oscillation wavelength range “WR41” of the optical amplifier 39. This is a characteristic in which the coupling efficiency is rapidly reduced.

  As a result, the light from the optical amplifier 40 that has propagated through the optical waveguide 42 and reached the demultiplexing / multiplexing region 44 enters the optical waveguide 43 with a coupling efficiency of about 80%, as indicated by “CH42” in FIG. The light is coupled and propagates through the optical waveguide 43.

  Thus, the light emitted from the optical amplifier 39 and the optical amplifier 40 propagating through the optical waveguide 43 is emitted from one end of the optical waveguide 43, and becomes plane parallel light by the waveguide lens function of the diffraction grating region 48.

  The diffracted light in the diffraction grating region 48 is incident on the reflector 47. Of the diffracted light incident on the reflector 47, the diffracted light from the diffraction grating perpendicularly incident on the reflector 47 becomes vertical reflected light from the reflector 47, and is diffracted by the diffraction grating 47 and is reflected in the diffraction grating region 48. The light is condensed by the waveguide type lens function and is incident on the other end of the waveguide 43 again. Diffracted light from the diffraction grating region that is not perpendicularly incident on the reflector 47 is reflected at different angles, so that even if it is diffracted by the diffraction grating region 48 and condensed by the waveguide type lens function of the diffraction grating region 48, the optical waveguide It is not incident on the other end of 43.

  The light that has propagated through the optical waveguide 43 and arrived at the demultiplexing / multiplexing region 44 enters the optical waveguide 41 or the optical waveguide 42 with a coupling efficiency of about 80% as shown by “CH41” or “CH42” in FIG. The light is coupled, propagates through the optical waveguide 41 or the optical waveguide 42, and enters the optical amplifier 39 or the optical amplifier 40.

  The reflected light from the reflection selecting means 53 is condensed by the waveguide type lens function of the diffraction grating region 48 and is incident on the other end of the optical waveguide 43 again.

  Of the reflected light from the reflection selection means that propagates through the optical waveguide 43 and reaches the demultiplexing / multiplexing region 44, the light in the wavelength range “WR41” is about 80% as shown by “CH41” in FIG. Is coupled to the optical waveguide 41 with a coupling efficiency of On the other hand, since the coupling efficiency to the optical waveguide 42 is reduced, the amount of light that propagates through the optical waveguide 42 and enters the optical amplifier 40 is very small.

  Similarly, the light in the wavelength range “WR42” among the reflected light from the reflection selection means that propagates through the optical waveguide 43 and reaches the demultiplexing / multiplexing region 44 is 80 as shown by “CH42” in FIG. It is coupled to the optical waveguide 42 with a coupling efficiency of about% and enters the optical amplifier 40. On the other hand, since the coupling efficiency to the optical waveguide 41 is reduced, the amount of light that propagates through the optical waveguide 41 and enters the optical amplifier 39 is very small.

  For this reason, the light that does not pass through the other output end of the optical amplifier 39 or the optical amplifier 40 that is not provided with the non-reflective film is not reflected by the reflector 47 and the other of the optical amplifier 39 or the optical amplifier 40 that is not provided with the non-reflective film The laser is oscillated by resonating with a resonator formed between the light emitting end of the first and second light emitting ends.

  On the other hand, the light that has propagated through the optical waveguide 43 and was not coupled to the optical waveguide 41 or the optical waveguide 42 in the demultiplexing / multiplexing region 44 propagates through the optical waveguide 43 as it is and is a non-reflective film indicated by “NR81” in FIG. The light is emitted from the other end of the optical waveguide 43 to which is applied.

  Thus, the light emitted from the other end of the optical waveguide 43 enters the optical fiber 30 via the lens 27, the optical isolator 28, and the lens 29, and is used for various measurements.

  In this state, when the wavelength control means (not shown) changes the angle of the reflector 47 around the rotation center, the diffraction angle of the diffracted light emitted from the diffraction grating region 48 perpendicularly incident on the reflector 47 Changes, the wavelength of laser oscillation changes. Further, since the resonator length of the resonator formed between the reflector 47 and the other emitting end of the optical amplifier 40 on which the non-reflective film is not applied changes, the resonance wavelength also changes.

  As a result, the outgoing light from one of the outgoing ends of the optical amplifier 39 and the optical amplifier 40 on which the non-reflective film is applied enters the optical waveguide 41 and the optical waveguide 42, and enters the optical waveguide 43 in the demultiplexing / multiplexing region 44. The combined light is incident on the wavelength selective reflection means 54, the reflected light from the wavelength selective reflection means 54 is incident on the optical waveguide 43 again, and the light coupled to the optical waveguide 41 or the optical waveguide 42 in the demultiplexing / multiplexing region 44 is obtained. A light is incident on the optical amplifier 39 or the optical amplifier 40 to form a resonator between the reflector 47 and the other output end of the optical amplifier 39 and the optical amplifier 40 on which the non-reflective film is not applied, and the angle of the reflector 47. By changing, the light emitted from two optical amplifiers having different wavelength ranges can be used, so that the wavelength variable range for laser oscillation can be expanded.

  Further, since the laser light incident on the optical fiber 30 is light whose wavelength is selected by the diffraction grating region 48 and the reflector 47, it becomes a low ASE light level laser light from which spontaneous emission light (ASE light) has been removed.

  Further, since the function of the waveguide lens 45 is combined with the diffraction grating region 48 as compared with the embodiment shown in FIG. 4, the optical system can be further downsized.

  As another configuration of the wavelength selective reflection means, as described in “Japanese Patent Laid-Open No. 2000-261886”, the central optical waveguide 43 is extended to the other end of the optical substrate 38 and highly reflected at the other end. A surface acoustic wave type wavelength filter may be provided on the optical waveguide 43 between the highly reflective film and the demultiplexing / multiplexing region 44 by forming a film.

  In this case, high-speed wavelength tuning is possible in a wide wavelength range, and no light is emitted to the optical substrate, so that optical axis adjustment is almost unnecessary.

  As the surface acoustic wave type wavelength filter, an acousto-optic tunable filter (AOTF) can be used.

  Further, the wavelength selective reflection means may have a configuration using a band pass filter and a reflector used in the prior art.

  Further, when the influence of the reflected return light from the output optical fiber 30 is slight, the lens 27, the optical isolator 28, and the lens 29 are unnecessary, and the optical fiber 30 is directly coupled to the other end of the optical waveguide 43. It does not matter.

  Incidentally, as a method of coupling the optical fiber 30 directly to the other end of the optical waveguide 43, a well-known technique using a V-groove structure can be used.

  In this case, further downsizing is possible, and passive alignment on the output light side (unaligned center fixing) is possible.

  Further, in the embodiment shown in FIG. 1 and the like, a structure in which three optical waveguides and two optical amplifiers are formed on one optical substrate is illustrated, but it is of course not limited to this structure. .

  Further, in the embodiment shown in FIG. 1 and the like, a planar third optical waveguide is formed on one optical substrate in a plane and in the central portion, and the first and second optical waveguides are formed on both sides of the third optical waveguide. Although the optical waveguides are formed in parallel and the intermediate portions of the first and second waveguides are illustrated as being adjacent to the third optical waveguide to form a demultiplexing / multiplexing region, of course, The structure is not limited.

1 is a block diagram showing a configuration of an embodiment of an external resonator type wavelength tunable light source according to the present invention. It is explanatory drawing (plan view) explaining the detail of an optical board | substrate. It is a characteristic curve figure which shows the relationship between the oscillation wavelength range of each optical amplifier, and the coupling efficiency of a demultiplexing / multiplexing area | region. It is a block diagram which shows the other Example of the external resonator type | mold wavelength variable light source which concerns on this invention. It is explanatory drawing (plan view) explaining the detail of an optical board | substrate. It is explanatory drawing (side view) explaining the detail of an optical board | substrate. It is a block diagram which shows the other Example of the external resonator type | mold wavelength variable light source which concerns on this invention. It is explanatory drawing (plan view) explaining the detail of an optical board | substrate. It is a block diagram which shows an example of the conventional external resonator type wavelength variable light source. It is a block diagram showing another example of a conventional external resonator type wavelength tunable light source.

Explanation of symbols

1, 12, 25, 26, 39, 40 Optical amplifier 2, 4, 6, 13, 15, 17, 22, 27, 29, 31 Lens 3, 14, 21, 28 Optical isolator 5, 16, 23, 30 Light Fiber 7, 19, 32 Diffraction grating 8, 20, 33, 47 Reflector 9 Rotation control means 10 Rotation drive means 11 Optical amplifier drive means 18 Beam splitter 24, 38, 38a Optical substrate 34, 35, 36, 41, 42, 43 Optical waveguide 37, 44 Demultiplexing / multiplexing area 45 Waveguide lens 46, 48 Diffraction grating area 50 Wavelength control means 51, 52, 53, 54 Wavelength selective reflection means

Claims (11)

In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
A first and a second optical amplifier each having a non-reflective film on one emission end and having different wavelength ranges;
A first and a second optical waveguide into which the outgoing light from one outgoing end to which the anti-reflective film of the first and second optical amplifiers is applied, respectively;
A third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region;
A lens that makes the outgoing light from one outgoing end of the third optical waveguide provided with the non-reflective film parallel light;
Wavelength selective reflection means for making the outgoing light from this lens incident and making the reflected light incident on one outgoing end of the third optical waveguide provided with the non-reflective film through the lens;
An external resonator type comprising: an optical fiber that emits light emitted from the other light emitting end of the third optical waveguide to which the non-reflective film is applied, and enters the light emitted from the other end. Tunable light source. In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
A first and a second optical amplifier each having a non-reflective film on one emission end and having different wavelength ranges;
A first and a second optical waveguide into which the outgoing light from one outgoing end to which the anti-reflective film of the first and second optical amplifiers is applied, respectively;
A third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region;
A first lens for making the emitted light from one emitting end of the third optical waveguide provided with the non-reflective film into parallel light;
Wavelength selective reflection means for allowing the outgoing light from the first lens to be incident and causing the reflected light to enter the one outgoing end of the third optical waveguide provided with the non-reflective film through the first lens. When,
A second lens that collimates outgoing light from the other outgoing end on which the non-reflective film of the third optical waveguide is applied;
An optical isolator to which parallel light from the second lens is incident;
A third lens for collecting the light emitted from the optical isolator;
An external resonator-type wavelength tunable light source, comprising: an optical fiber that emits light emitted from the third lens at one end and outputs light from the other end. The wavelength selective reflection means is
A reflector whose angle is variable around the center of rotation;
The incident parallel light is emitted as diffracted light to the reflector, and the reflected light from the reflector is provided with a non-reflective film of the third optical waveguide via the lens or the first lens. 3. An external resonator type wavelength tunable light source according to claim 1, wherein the external resonator type wavelength tunable light source comprises a diffraction grating that is incident on one of the output ends. In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
A first and a second optical amplifier each having a non-reflective film on one emission end and having different wavelength ranges;
A first and a second optical waveguide into which the outgoing light from one outgoing end to which the anti-reflective film of the first and second optical amplifiers is applied, respectively;
A third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region;
Wavelength selective reflection means for allowing the outgoing light from one outgoing end of the third optical waveguide to enter and the reflected light to enter one outgoing end of the third optical waveguide;
An external resonator type comprising: an optical fiber that emits light emitted from the other light emitting end of the third optical waveguide to which the non-reflective film is applied, and enters the light emitted from the other end. Tunable light source. In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
A first and a second optical amplifier each having a non-reflective film on one emission end and having different wavelength ranges;
A first and a second optical waveguide into which the outgoing light from one outgoing end to which the anti-reflective film of the first and second optical amplifiers is applied, respectively;
A third optical waveguide in which light propagating through the first and second optical waveguides is coupled by a demultiplexing / multiplexing region;
Wavelength selective reflection means for allowing the outgoing light from one outgoing end of the third optical waveguide to enter and the reflected light to enter one outgoing end of the third optical waveguide;
A first lens that collimates outgoing light from the other outgoing end of the third optical waveguide provided with the non-reflective film;
An optical isolator to which the parallel light from the first lens is incident;
A second lens for collecting the light emitted from the optical isolator;
An external resonator-type wavelength tunable light source, comprising: an optical fiber in which light emitted from the second lens enters one end and outputs light from the other end. The wavelength selective reflection means is
A waveguide-type lens formed in a slab optical waveguide that converts light emitted from the third optical waveguide into plane parallel light;
A reflector whose angle is variable around the center of rotation;
A slab that emits the plane parallel light incident from the waveguide type lens as diffracted light to the reflector and makes the reflected light from the reflector enter the third optical waveguide via the waveguide type lens. 6. The external resonator type wavelength tunable light source according to claim 4 or 5, comprising a diffraction grating region formed in the optical waveguide. The wavelength selective reflection means is
A reflector whose angle is variable around the center of rotation;
The light emitted from the third optical waveguide is converted into plane parallel light, the plane parallel light is emitted as diffracted light to the reflector, and the reflected light from the reflector is condensed to form the third optical waveguide. 6. An external resonator type wavelength tunable light source according to claim 4 or 5, comprising a diffraction grating region formed in a slab optical waveguide that is incident on the slab. The third optical waveguide formed on the optical substrate;
On the optical substrate, the first and second optical waveguides are formed in parallel on both sides of the third optical waveguide, and the intermediate portions are adjacent to the third optical waveguide to constitute the demultiplexing / multiplexing region. The external resonator type wavelength tunable light source according to any one of claims 1 to 3, further comprising two optical waveguides. The third optical waveguide formed on the optical substrate;
On the optical substrate, the first and second optical waveguides are formed in parallel on both sides of the third optical waveguide, and the intermediate portions are adjacent to the third optical waveguide to constitute the demultiplexing / multiplexing region. Two optical waveguides;
7. The external resonator type wavelength tunable light source according to claim 6, further comprising the waveguide lens and the diffraction grating region formed on the optical substrate and in a slab optical waveguide. The third optical waveguide formed on the optical substrate;
On the optical substrate, the first and second optical waveguides are formed in parallel on both sides of the third optical waveguide, and the intermediate portions are adjacent to the third optical waveguide to constitute the demultiplexing / multiplexing region. Two optical waveguides;
8. The external resonator type tunable light source according to claim 7, further comprising: the diffraction grating region formed on the optical substrate and in a slab optical waveguide. In an external resonator type tunable light source that changes the wavelength by an optical amplifier and wavelength selective reflection means arranged outside the optical amplifier,
A first and a second optical amplifier each having a non-reflective film on one emission end and having different wavelength ranges;
A first and a second optical waveguide into which the outgoing light from one outgoing end to which the anti-reflective film of the first and second optical amplifiers is applied, respectively;
A third optical waveguide having a highly reflective film applied to one end where the light propagating through the first and second optical waveguides is coupled by the demultiplexing / multiplexing region;
A surface acoustic wave type wavelength filter provided between the one end where the highly reflective film of the third optical waveguide is applied and the demultiplexing / multiplexing region;
An external resonator type comprising: an optical fiber that emits light emitted from the other light emitting end of the third optical waveguide to which the non-reflective film is applied, and enters the light emitted from the other end. Tunable light source.

Images