JP2011095609A - Optical control delay device and spectral device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical control delay device which is hardly affected by disturbance and is small-sized while maintaining accuracy and is capable of easily controlling a delay, and a spectral device. <P>SOLUTION: The optical control delay device includes a demultiplexer 5 for branching light, a first wavelength converter 1 on which one of light beams branched by the demultiplexer 5 is made incident, an optical delay device 2 to which pulse light of which the wavelength has been converted by the first wavelength converter 1 is inputted, and a second wavelength converter 3 for converting the wavelength of the pulse light delayed by the optical delay device 2. The optical delay device 2 delays the incident light by a delay varied in accordance with the wavelength of the incident light and controls the time lag between the remaining light beam branched by the demultiplexer 5 and light which is made incident on the first wavelength converter 1 and is outputted via the optical delay device 2 and the second wavelength converter 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical control delay device and the like. More specifically, the present invention relates to a light control delay device and a spectroscopic device that can control the delay amount by controlling the wavelength of incident light. The present invention also relates to a light control delay device and a spectroscopic device that can be used for generation and detection of electromagnetic waves in the terahertz region (100 GHz to 10 THz) and spectroscopy using ultrashort light pulses.

2. Description of the Related Art In the fields of optical communication and physical property research, optical signals that change within a time on the order of femtoseconds ( ^10-15 seconds) to picoseconds ( ^10-12 seconds) are actively used. Such a change in the optical signal can be measured by time-resolved spectroscopic measurement with high time resolution. Therefore, a highly accurate spectroscopic device is desired.

  FIG. 1 is a block diagram showing a configuration example of a conventional optical delay controller. As shown in FIG. 1, a conventional optical delay controller 101 includes a mode-locked laser 102 that is an ultrashort optical pulse laser, a beam splitter 103 that splits the laser light, a mechanically driven movable mirror 104, and an optical device. An intensity modulator 105 is included. Then, the pulse light from one ultrashort optical pulse laser is branched into two or more by a beam splitter. Then, by reflecting one pulsed light with a movable mirror, the arrival time at an arbitrary position with respect to the other light pulse is changed (Non-Patent Document 1). This optical delay controller has problems such as inaccurate timing control due to the mechanical accuracy of the movable stage, a long measurement time, or all branched pulsed light having the same wavelength.

  FIG. 2 is a block diagram showing a configuration example of a conventional optical delay controller, which is different from that shown in FIG. As shown in FIG. 2, there is a conventional optical delay controller 111 having two ultrashort optical pulse lasers 112 and 113. This optical delay controller changes the arrival time of an optical pulse at an arbitrary position by precisely controlling the cavity length of one or both ultrashort optical pulse lasers and operating them at different repetition frequencies. (Non-patent document 2). In this optical delay controller, the cavity length control mechanism for obtaining different repetition frequencies is complicated, timing jitter exists independently for each optical pulse laser, and there are difficulties in energy resolution, accuracy and SN ratio. There was a problem that the mechanism to control it was complicated.

In addition, these conventional optical delay controllers require precise control of the optical system, so they are vulnerable to disturbances due to environmental changes (for example, temperature changes and vibrations), and the repetition frequency is almost fixed. And the drawbacks were large equipment.
Ultra fast Spectroscopy of Semiconductors and Semiconductor Nanostructures, section 1.3 Applied Physics Letters, vol. 87, p061101 (2005)

  An object of the present invention is to provide an optical control delay device and a spectroscopic device that are not easily affected by disturbance.

  An object of the present invention is to provide a light control delay device and a spectroscopic device that can adjust the delay time in a small size and easily while maintaining accuracy.

  The present invention is based on the knowledge that an optically controlled delay device that can easily control the delay amount can be provided by using an optical delay device that can change the delay amount according to the wavelength. In particular, the present invention is based on the knowledge that an optical control delay device that is less susceptible to disturbance can be provided by using an optical delay device that generates a delay by utilizing group velocity dispersion in a dispersion medium. .

  The optical control delay device according to the first aspect of the present invention includes a demultiplexer 5 for demultiplexing light, a first wavelength converter 1 on which one light demultiplexed by the demultiplexer 5 is incident, An optical delay device 2 to which pulsed light whose wavelength has been converted by the first wavelength converter 1 is input, and a second wavelength converter for converting the wavelength of the pulsed light delayed by the optical delay device 2 3 and so on. The optical delay device 2 has a different delay amount to the incident light depending on the wavelength of the incident light, and the remaining light demultiplexed by the demultiplexer 5 is incident on the first wavelength converter 1. , The delay time between the light output through the optical delay device 2 and the second wavelength converter 3 can be controlled.

In this way, by using an optical delay device that varies the amount of delay given to the incident light depending on the wavelength of the incident light, it is not necessary to perform precise control of the optical system, so that a small and simple optical control delay device can be provided. . In addition, it is possible to provide an optical control delay device that is not easily affected by disturbance. Further, between the remaining light demultiplexed by the demultiplexer 5 and the light incident on the first wavelength converter 1 and output through the optical delay device 2 and the second wavelength converter 3. Since an optically controlled delay device that can control the delay time can be provided, simple time-resolved measurement can be realized.

  In a preferred embodiment of the optical control delay device according to the first aspect of the present invention, the second wavelength converter 3 is configured so that the wavelength of the output light becomes the wavelength of the light incident on the first wavelength converter 1. The optical control delay device as described above, which changes the wavelength of incident light.

  The second wavelength converter 3 is demultiplexed by the demultiplexer 5 by changing the wavelength of the incident light so that the wavelength of the output light is the same as the light incident on the first wavelength converter 1. Since it becomes the same as the wavelength of one light, time-resolved measurement can be performed by the optical control delay device of the present invention.

  The preferred embodiment of the optical control delay device according to the first aspect of the present invention further includes an optical pulse generator 4 for generating pulsed light incident on the demultiplexer 5, and the optical pulse generator 4 has a mode The optical control delay device according to any one of the above, including a synchronous fiber laser.

  By using a mode-locked fiber laser as the optical pulse generator 4, an optical pulse generator in which the oscillation frequency and the pulse repetition frequency are accurately fixed can be obtained.

  The preferred embodiment of the optical control delay device according to the first aspect of the present invention further includes an optical pulse generator 4 for generating pulsed light incident on the demultiplexer 5. The optical control delay device according to any one of the above, including a comb generator.

By using the optical comb generator as the optical pulse generator 4, it is possible to simultaneously generate a plurality of optical frequency components having a frequency difference of equal intervals, and it is possible to obtain an optical pulse generator that is accurately fixed.

  The preferred embodiment of the optical control delay device according to the first aspect of the present invention further includes an optical pulse generator 4 for generating pulsed light incident on the branching filter 5, and the optical pulse generator 4 is a semiconductor. The optical control delay device according to any one of the above, including a quantum dot comb laser.

  By using a semiconductor quantum dot comb laser as the optical pulse generator 4, an optical pulse generator in which the oscillation frequency and the pulse repetition frequency are accurately fixed can be obtained.

  In a preferred aspect of the optical control delay device according to the first aspect of the present invention, the optical control delay according to any one of the above, wherein the first wavelength converter 1 is a wavelength converter using a semiconductor optical amplifier. It is a vessel.

  By using a semiconductor optical amplifier as the first wavelength converter 1, it is possible to perform wavelength conversion by performing cross-phase modulation with pulsed light and adjustment light.

A preferred embodiment of the optically controlled delay device according to the first aspect of the present invention is such that the first wavelength converter 1 includes a semiconductor optical amplifier, and mixes the adjusted light having a controlled frequency and the incident light, The optical control delay device according to any one of the above, which is a wavelength converter that converts a wavelength of output light. By controlling the frequency of the adjustment light, the wavelength of the output light is controlled, thereby controlling the delay amount given by the optical delay device 2.

The first wavelength converter 1 including the semiconductor optical amplifier controls the frequency of the adjustment light incident for wavelength conversion and changes the frequency. By changing the frequency of the adjustment light, the delay amount given to the optical delay device can be changed, so that an optical control delay device that can easily control the delay time can be provided.

A preferred embodiment of the optical control delay device according to the first aspect of the present invention is the optical control delay device according to any one of the above, wherein the first wavelength converter 1 is an optical fiber.

  By using an optical fiber as the first wavelength converter 1, wavelength conversion can be performed by nonlinear optical effects such as four-wave mixing, self-phase modulation, cross-phase modulation, or Raman spectroscopy.

A preferred embodiment of the optical control delay device according to the first aspect of the present invention is a wavelength converter using a semiconductor element in which the first wavelength converter 1 converts the wavelength of incident light by four-wave mixing. The optical control delay device according to any one of the above.

  Examples of the semiconductor element include a gallium aluminum arsenide (GaAlAs) semiconductor element, a distributed feedback (DFB) laser, a distributed reflection (DBR) laser, and a quantum dot laser. By using these semiconductor elements as nonlinear optical elements, wavelength conversion can be performed by four-wave mixing.

  The optical control delay device according to the second aspect of the present invention includes a first wavelength converter 1, an optical delay device 2 to which pulsed light whose wavelength has been converted by the first wavelength converter 1, and an optical delay device. And a second wavelength converter 3 for converting the wavelength of the pulsed light delayed by the delay device 2. The optical delay device 2 differs in the amount of delay given to the incident light depending on the wavelength of the incident light.

By changing the wavelength of the incident light by the wavelength conversion by the first wavelength converter 1, the delay amount given to the incident light by the optical delay device 2 can be varied, and the delay amount can be easily controlled. .

  A preferred embodiment of the optical control delay device according to the second aspect of the present invention is that the adjustment light incident on the first wavelength converter 1 to convert the wavelength of the pulsed light, and the second wavelength converter 3 The light control delay device according to the above, in which the wavelength of the incident adjustment light is the same.

Even if the adjustment light incident on the first wavelength converter 1 and the adjustment light incident on the second wavelength converter 3 are configured to have the same wavelength, the pulse output from the second wavelength converter 3 The wavelength of the light is the wavelength of the pulsed light that enters the first wavelength converter. Therefore, a simpler light control delay device can be obtained.

  The third aspect of the present invention relates to an optical control delay device having a folding means 22. More specifically, this optical control delay device includes a demultiplexer / multiplexer 20 that demultiplexes and multiplexes light, and wavelength conversion in which one light demultiplexed by the demultiplexer / multiplexer 20 enters. , Optical delay device 2 to which the light whose wavelength has been converted by wavelength converter 21 is input, first return means 22 for returning output light from optical delay device 2, and demultiplexing / multiplexing And second folding means 23 for folding the remaining light demultiplexed by the multiplexer 20 toward the demultiplexing / multiplexing device 20.

  Since it has such a configuration, the light (first light) that has been demultiplexed by the demultiplexing / multiplexing unit 20 and folded back toward the demultiplexing / multiplexing unit 20 by the second folding unit 23; Light that enters the wavelength converter 21, passes through the optical delay device 2, is turned up by the turn-back means 22, passes through the optical delay device 2 and the wavelength converter 21, and is output to the demultiplexing / multiplexing device 20 2) is multiplexed by the demultiplexer / multiplexer 20. The delay time between these lights (first light and second light) can be controlled.

  The optical control delay device according to the fourth aspect of the present invention includes a demultiplexer 5 that demultiplexes light, a wavelength converter 21 into which one light demultiplexed by the demultiplexer 5 enters, and a wavelength converter 21. The optical delay device 2 to which the pulse light whose wavelength has been converted by the optical delay device 2 is input, the return device 22 for returning the output light from the optical delay device 2, and the circulator located between the duplexer 5 and the wavelength converter 21 25. The optical delay device 2 differs in the amount of delay given to the incident light depending on the wavelength of the incident light. Since it has such a configuration, the remaining light demultiplexed by the demultiplexer 5; enters the wavelength converter 21, passes through the optical delay device 2, is folded by the folding means 22, and is combined with the optical delay device 2 and the wavelength. The delay time between the light output to the duplexer 5 via the converter 21 can be controlled. The circulator 25 outputs the incident light toward the wavelength converter 21 when one of the lights demultiplexed by the demultiplexer 5 enters the circulator 25. On the other hand, when the circulator 25 is turned back by the turn-back means 22 and the light output to the wavelength converter 21 through the optical delay device 2 again enters the circulator 25, the circulator 25 outputs the light so as not to return to the wavelength converter 21.

  A fifth aspect of the present invention is a spectroscopic device including any one of the light control delay devices described above. A spectroscopic device that can perform time-resolved spectroscopic measurement by arbitrarily setting a delay time can be obtained by using the spectroscopic device to which any of the above-described optical control delay devices is applied.

According to the present invention, it is possible to provide an optical control delay device and a spectroscopic device that are not easily affected by disturbance.

  According to the present invention, it is possible to provide a light control delay device and a spectroscopic device that can control the delay amount in a small size and easily while maintaining accuracy.

FIG. 1 is a block diagram showing a configuration example of a conventional optical delay controller. FIG. 2 is a block diagram showing a configuration example of a conventional optical delay controller, which is different from that shown in FIG. FIG. 3 is a block diagram for explaining the basic configuration of the optical delay controller according to the present invention. FIG. 4 is a block diagram for explaining the optical delay controller according to the first embodiment of the present invention. FIG. 5 is a block diagram for explaining an optical delay controller according to the second embodiment of the present invention. FIG. 6 is a diagram for explaining the principle of wavelength conversion. FIG. 7 is a block diagram for explaining the basic configuration of an optical delay controller according to the present invention. FIG. 8 is a block diagram for explaining the basic configuration of an optical delay controller according to the present invention.

  Hereinafter, the present invention will be specifically described with reference to the drawings. The present invention is not limited to the embodiments of the present invention described below, and includes configurations that can be appropriately modified within the scope obvious to those skilled in the art. FIG. 3 is a block diagram for explaining the basic configuration of the optical delay controller according to the present invention. As shown in FIG. 3, the present invention includes a demultiplexer 5 for demultiplexing light, a first wavelength converter 1 on which one light demultiplexed by the demultiplexer 5 is incident, An optical delay device 2 to which the pulsed light whose wavelength has been converted by the wavelength converter 1 is input, and a second wavelength converter 3 for converting the wavelength of the pulsed light delayed by the optical delay device 2. Have. The optical delay device 2 has a different delay amount to the incident light depending on the wavelength of the incident light, and the remaining light demultiplexed by the demultiplexer 5 is incident on the first wavelength converter 1. , An optical control delay device capable of controlling the delay time between the light output via the optical delay device 2 and the second wavelength converter 3.

  An optical delay controller is a device that can provide a controlled time delay to an optical signal. Examples of the optical delay controller include those disclosed in Non-Patent Documents 1 and 2 above, and those disclosed in Japanese Patent Application Laid-Open No. 2009-65570 and Japanese Patent Application Laid-Open No. 10-224325. These are incorporated herein by reference. The optical delay controller of the present invention can be preferably used for an apparatus that can give a controlled time delay to one of two optical signals.

  The duplexer 5 divides the incident light into two, one light is incident on the first wavelength converter 1 and the other is output as it is. When the present invention is applied to a time-resolved spectroscopic system based on pump-probe measurement, light incident on the first wavelength converter 1 is probe light, and the other light output as it is is pump light. The duplexer 5 is, for example, a beam splitter.

The first wavelength converter 1 receives one of the lights demultiplexed by the demultiplexer 5 and converts the wavelength of the incident light. Specifically, by using the adjustment light for controlling the frequency of the incident pulse light _{(λ 1) (λ p1)} , by changing the wavelength of the pulsed light (lambda _1), the light wavelength is converted ( λ ₂ ) is output. The first wavelength converter 1 is constituted by, for example, a semiconductor optical amplifier.

  A wavelength converter using a semiconductor optical amplifier (SOA) is used in, for example, a wavelength division multiplexing communication system. Examples of wavelength converters using a semiconductor optical amplifier (SOA) are those disclosed in Japanese Patent Application Laid-Open No. 2008-224862 or Japanese Patent Application Laid-Open No. 2006-78530. These documents are incorporated herein by reference.

The first wavelength converter 1 may be one using a nonlinear optical crystal having a birefringence. A wavelength converter using a nonlinear optical crystal having such a birefringence is widely used, for example, in a wavelength conversion laser light source. Examples of nonlinear optical crystals having a birefringence include LiB ₃ O ₅ (lithium triborate: LBO), KTiOPO ₄ (potassium titanyl phosphate: KTP), CsLiB ₆ O ₁₀ (cesium lithium borate: CLBO) polarization inversion structure. LiNbO ₃ (lithium niobate: PPLN) and LiTaO ₃ (lithium tantalate: PPLT) formed. Of these, PPLN is preferred. Examples of wavelength converters using PPLN are those disclosed in Japanese Patent Application Laid-Open No. 2009-122606 or Japanese Patent Application Laid-Open No. 2008-098773. These documents are incorporated herein by reference.

  The first wavelength converter 1 may be a silicon-based semiconductor that uses a sum frequency, a difference frequency, or a parametric effect. Examples of wavelength converters using silicon-based semiconductors are those disclosed in Japanese Patent Application Laid-Open No. 2008-209522 or Japanese Patent Application Laid-Open No. 2004-70338. These documents are incorporated herein by reference.

The optical delay device 2 gives a delay to the light incident on the optical delay device 2. Examples of the optical delay device 2 include a dispersion medium, specifically, an optical fiber. The optical delay device 2 generates a time delay using group velocity dispersion in the dispersion medium. That is, when pulsed light is incident on the dispersion medium, a desired time delay can be obtained by group velocity dispersion in the dispersion medium. When the group delay in the dispersion medium is G (ps / km) and the length of the medium is L (km), the delay amount D (ps) can be expressed by the following equation (1).
D = G × L (1)

Therefore, the pulsed light that has passed through the dispersion medium of the optical delayer 2 through the first wavelength converter 1 is delayed by D (ps) compared with the remaining pulsed light that has been demultiplexed by the demultiplexer 5. Will be emitted. Further, since the refractive index of the dispersion medium changes depending on the wavelength of light incident on the dispersion medium, the delay amount D also changes. That is, even if the dispersion medium has the same length L, the delay amount D can be changed by changing the wavelength of light incident on the dispersion medium. Therefore, the delay amount D can be controlled by changing the wavelength of the pulsed light incident on the optical delay device 2 by the first wavelength converter 1.

In this way, it is not necessary to perform precise control of the optical system mechanically by using an optical delay device that varies in the amount of delay given to the incident light depending on the wavelength of the incident light, so that a small and simple optical control delay device can be used. Can provide. In addition, it is possible to provide an optical control delay device that is not easily affected by disturbance. Further, between the remaining light demultiplexed by the demultiplexer 5 and the light incident on the first wavelength converter 1 and output through the optical delay device 2 and the second wavelength converter 3. An optical control delay device capable of arbitrarily setting the delay time can be provided. Further, since an optical fiber is used as the dispersion medium, light can be freely routed.

  Another example of the optical delay device 2 is a waveguide, a photonic crystal waveguide, a photonic crystal fiber, a grating pair, or a prism pair (for example, JP-T-2008-537342) manufactured on a dielectric or semiconductor. And a grating pair in JP-A-6-088976) and an arrayed waveguide grating.

  An example of an arrayed waveguide grating (AWG) is disclosed in Japanese Patent Application Laid-Open No. 2009-200733. The AWG has an input slab coupler, an output slab coupler, and a plurality of optical waveguides. The input slab coupler is a slab waveguide connected to a plurality of input ports. The output slab coupler is a slab waveguide into which light from the input slab coupler is input. The input slab coupler and the output slab coupler are optically connected by a plurality of optical waveguides. Each optical waveguide is different in length by a predetermined amount, and can be given to an optical signal passing through a time delay corresponding to the difference in path length. The time delay given here depends on the wavelength.

The second wavelength converter 3 receives the pulsed light output from the optical delay device 2 and converts the wavelength of the incident light. Specifically, the adjustment light (λ _p2 ) for controlling the frequency of the incident pulsed light (λ ₂ ) is used to change the wavelength of the pulsed light (λ ₂ ), and the light whose wavelength has been converted is changed. Output. The second wavelength converter 3 is composed of a semiconductor element such as a semiconductor optical amplifier, an optical fiber, or a quantum dot laser, for example. Preferably, the second wavelength converter 3 changes the wavelength of the incident light so that the wavelength of the output light becomes the wavelength of the light incident on the first wavelength converter 1. The second wavelength converter 3 changes the wavelength of the incident light so that the wavelength of the output light is the same as the light (λ ₁ ) incident on the first wavelength converter 1. Since it becomes the same as the wavelength of one of the demultiplexed lights, the light control delay device of the present invention can constitute a spectroscopic device to perform time-resolved measurement.

In a preferred embodiment, the adjustment light (λ _p1 ) incident on the first wavelength converter 1 and the adjustment light (λ _p2 ) incident on the second wavelength converter 3 in order to convert the wavelength of the pulsed light. Let the wavelength be the same. By configuring the adjustment light incident on the first wavelength converter 1 and the adjustment light incident on the second wavelength converter 3 to have the same wavelength, a simpler light control delay device can be obtained. .

  Also, as shown in FIG. 3, a preferred embodiment of the present invention is the above-described optical control delay device having an optical pulse generator 4 for generating pulsed light incident on the duplexer 5. . The pulsed light generated from the optical pulse generator 4 is demultiplexed by the demultiplexer 5, enters the first wavelength converter 1, and is output through the optical delay unit 2 and the second wavelength converter 3. Time-resolved measurement is performed with one light and the remaining light demultiplexed by the demultiplexer.

  An example of a pulsed light source is one using a continuous light (CW) light source. The optical band may be not only the C-band but also the L-band on the long wave side or the S-band on the short wave side. The light intensity is 1 mW to 50 mW.

  Specifically, an example of a pulsed light source uses a mode-locked fiber laser. An example of a mode-locked fiber laser is an ultrashort optical pulse laser such as a femtosecond laser. Examples of the optical pulse laser are a fiber mode-locked laser doped with Er and a fiber mode-locked laser doped with Yb. By using a mode-locked fiber laser as the optical pulse generator 4, an optical pulse generator in which the oscillation frequency and the pulse repetition frequency are accurately fixed can be obtained. An example of a pulsed light source using a mode-locked fiber laser is disclosed in Japanese Unexamined Patent Application Publication No. 2009-064940 or Japanese Unexamined Patent Application Publication No. 2008-311629. These are incorporated herein by reference.

  Another preferred embodiment of the optical pulse generator 4 includes an optical comb generator. The optical comb generator simultaneously generates a plurality of optical frequency components having a frequency difference of equal intervals. Optical frequency comb generators are already known. Examples of optical pulse generators including optical comb generators are those disclosed in Japanese Patent Application Laid-Open No. 2007-219323 or Japanese Patent Application Laid-Open No. 10-083004. These are incorporated herein by reference.

By using the optical comb generator as the optical pulse generator 4, it is possible to simultaneously generate a plurality of optical frequency components having a frequency difference of equal intervals, and it is possible to obtain an optical pulse generator that is accurately fixed.

  Yet another preferred embodiment of the optical pulse generator 4 includes a semiconductor quantum dot comb laser. The semiconductor quantum dot comb laser is a semiconductor laser having a quantum well structure in which a strained quantum well is introduced into an active layer. A semiconductor quantum dot comb laser is also called a semiconductor quantum dot laser. For example, a semiconductor laser having a quantum well structure using InGaAs or InGaAsP can be mentioned. Further, it may be a quantum well structure and may be a distributed feedback semiconductor laser (DFB laser). An example of the optical pulse generator 4 including a semiconductor quantum dot comb laser includes a semiconductor quantum dot comb laser and a circuit disclosed in Japanese Patent Publication No. 2007-52512. This document is incorporated herein by reference.

  By using a semiconductor quantum dot comb laser as the optical pulse generator 4, an optical pulse generator in which the oscillation frequency and the pulse repetition frequency are accurately fixed can be obtained.

The operation of the optical control delay device according to the present invention will be described with reference to FIG. The pulse light (λ ₁ ) generated by the optical pulse generator 4 is demultiplexed by the demultiplexer 5, and one wave is input to the first wavelength converter 1. The first wavelength converter 1 changes the wavelength of the pulsed light (λ ₁ ) using the adjustment light (λ _p1 ) and outputs the light (λ ₂ ) whose wavelength has been converted. The converted light (λ ₂ ) enters the optical delay device 2. The optical delay device 2 provides the light (λ ₂ ) with the delay amount D determined by the above-described equation and outputs the light. The output light (λ ₂ ) is input to the second wavelength converter 3, the wavelength of the pulsed light (λ ₂ ) is changed using the adjustment light (λ _p2 ), and the wavelength-converted light (λ ₁ ) is output. The light converted and output by the second wavelength converter 2 has the same wavelength as the light incident on the first wavelength converter, but is delayed by the delay amount D by the optical delay device 2. . That is, since the light of the same wavelength delayed by the delay amount D is output as compared with the remaining light that has been demultiplexed by the demultiplexer 5 and not incident on the first wavelength converter 3, time-resolved spectroscopy Can be performed easily.

  FIG. 4 is a block diagram for explaining the optical delay controller according to the first embodiment of the present invention. The configurations of the optical pulse generator 4, the demultiplexer 5 and the optical delay device 2 are the same as those in FIG. The optical control delay device according to the present embodiment is a wavelength converter in which the first wavelength converter 1 includes a semiconductor optical amplifier 6. By using the first wavelength converter 1 including a semiconductor optical amplifier, it is possible to perform wavelength conversion by performing cross-phase modulation with pulsed light and adjustment light.

The first wavelength converter 1 controls the wavelength of the output light by controlling the frequency of the adjustment light, thereby controlling the delay amount given by the optical delay device 2. The first wavelength converter 1 including the semiconductor optical amplifier controls the frequency of the adjustment light incident for wavelength conversion and changes the frequency. By changing the frequency of the adjustment light, the delay amount given to the optical delay device can be changed, so that an optical control delay device that can easily control the delay time can be provided.

As shown in FIG. 4, the first wavelength converter 1 in the optical delay controller of the present embodiment includes a first semiconductor optical amplifier 6 and a circulator 7. Since the semiconductor optical amplifier (SOA) 6 has a wide wavelength variable range, the variable range of the delay amount can be increased. Furthermore, the light output from the semiconductor optical amplifier can be amplified.

The operation of the optical delay controller according to this embodiment will be described. The pulse light (λ ₁ ) generated by the pulse generator 4 is demultiplexed by the demultiplexer 5, and one wave is input to the first semiconductor optical amplifier 6 of the first wavelength converter 1. The first semiconductor optical amplifier 6 is connected to the circulator 7, and pulsed light (λ ₁ ) is input to the first semiconductor optical amplifier 6. In order to adjust the wavelength of the pulsed light incident on the optical delay device 2, adjusted light (λ _p1 ) whose frequency is controlled is input to the circulator 7. The adjustment light (λ _p1 ) input to the circulator 7 is input to the first semiconductor optical amplifier 6 so as to face the pulsed light. In the first semiconductor optical amplifier 6, mutual gain modulation occurs between the pulsed light and the adjustment light, wavelength conversion is performed, and light (λ ₂ ) logically inverted from the pulsed light is output from the first semiconductor optical amplifier 6. Is done. The output light (λ ₂ ) is input to the optical delay device 2 via the circulator 7. Note that before the adjustment light (λ _p1 ) is input to the first semiconductor optical amplifier 6, for example, the polarization controller may adjust the wavelength conversion efficiency to be optimum. Further, in order to make only the output light (λ ₂ ) out of the output light from the circulator 7 enter the optical delay device 2 effectively, the light (λ ₂ ) is interposed between the circulator 7 and the optical delay device 2. A band-pass filter having a transmission region in a region including may be provided.

Second wavelength converter 3, optical delay output from the pulse light (lambda ₂₎ and a multiplexer 8 and the adjustment light (lambda _p2) is input, the pulsed light (lambda ₂₎ and the adjustment light ( λ _p2 ), a second semiconductor optical amplifier 9 that performs cross-phase modulation, a first polarizer 10 to which light output from the second semiconductor optical amplifier 9 is input, and light that has passed through the polarizer 10 And a birefringent element 11 that delays the light and a second polarizer 12 that passes light output from the birefringent element. Wavelength conversion is performed so that the wavelength of the output light is the same as that of the pulsed light (λ ₁ ) incident on the first wavelength converter 1.

The second semiconductor optical amplifier 9 performs cross-phase modulation between the pulsed light (λ ₂ ) and the adjustment light (λ _p2 ). For this reason, the phase of the light output from the second semiconductor optical amplifier 9 has changed. The light transmitted through the first polarizer 10 is input to the birefringent element 11. As the birefringent element 11, for example, a polarization maintaining fiber or calcite is used, and a difference in propagation speed between two axes (fast axis and slow axis) is used. The light propagating through the birefringent element 9 causes a phase shift in the phase change between the fast axis direction and the slow axis direction. The second polarizer 12 converts the phase modulation into intensity modulation by passing only the section in which the time lag has occurred between the fast axis direction and the slow axis direction. The converted light is separated into adjustment light (λ _p2 ) and pulsed light (λ ₁ ) using a bandpass filter (not shown). The output pulsed light (λ ₁ ) is light obtained by logically inverting the pulsed light (λ ₂ ) input to the second wavelength converter 3.

  The first semiconductor optical amplifier 6 and the second semiconductor optical amplifier 9 can be constituted by, for example, a semiconductor optical amplifier using quantum dots as an active layer, or a semiconductor optical amplifier having a quantum well structure.

FIG. 5 is a block diagram for explaining an optical delay controller according to the second embodiment of the present invention. The configurations of the optical pulse generator 4, the demultiplexer 5 and the optical delay device 2 are the same as those in FIG. As shown in FIG. 5, in the optical control delay device according to the second embodiment of the present invention, the first wavelength converter 1 is composed of a first nonlinear optical element 13 and a first optical wavelength filter 14. The second wavelength converter 3 configured is a light control delay device having a second nonlinear optical element 15 and a second optical wavelength filter 16. By using a nonlinear optical element, wavelength conversion is performed by a nonlinear optical effect such as four-wave mixing, self-phase modulation, cross-phase modulation, or Raman spectroscopy.

For example, optical fibers are used as the first nonlinear optical element 13 and the second nonlinear optical element 14. Further, a semiconductor element may be used. Examples of the semiconductor element include a gallium / aluminum arsenide (GaAlAs) semiconductor element, a distributed feedback (DFB) laser, a distributed reflection (DBR) laser, and a quantum dot laser. By using these semiconductor elements as nonlinear optical elements, wavelength conversion can be performed by nonlinear optical effects such as four-wave mixing, self-phase modulation, cross-phase modulation, or Raman spectroscopy.

An example of a wavelength conversion method using four-wave mixing is a method disclosed in Japanese Patent Application Laid-Open No. 2007-226076 or Japanese Patent Application Laid-Open No. 2006-106440. Examples of wavelength conversion using self-phase modulation are the methods disclosed in Japanese Patent Application Laid-Open No. 2003-194713 or Japanese Patent Application Laid-Open No. 2001-156715. Examples of wavelength conversion using cross-phase modulation are the methods disclosed in Japanese Patent Application Laid-Open No. 2006-251360, Japanese Patent Application Laid-Open No. 2006-078530, or Japanese Patent Application Laid-Open No. 2004-020982. An example of a wavelength conversion method using Raman spectroscopy is a method disclosed in Japanese Patent Application Laid-Open No. 2004-163558 or Japanese Patent Application Laid-Open No. 2002-229086. These documents are incorporated herein by reference.

The first optical wavelength filter 14 and the second optical wavelength filter 16 are filters that transmit only light having a certain range or specific wavelength, and are, for example, bandpass filters. In the present embodiment, the first optical wavelength filter 14 and the second optical wavelength filter 16 transmit only the light generated by the four-wave mixing and the light generated from the adjustment light (so-called idler light). Designed to be

The operation when the four-wave mixing method is used in the optical delay controller of this embodiment will be described. The pulsed light (λ ₁ ) generated by the pulse generator 4 is demultiplexed by the demultiplexer 5, and one of the waves is input to the first nonlinear optical element 13 of the first wavelength converter 1. The first nonlinear optical element 13 is supplied with the adjustment light (λ _p1 ) whose frequency is controlled in order to convert the wavelength of the pulse light together with the pulse light (λ ₁ ). In the first nonlinear optical element 13, four-wave mixing is performed using pulsed light and adjustment light. As a result, the first nonlinear optical element 13 outputs three lights of pulsed light (λ ₁ ), adjustment light (λ _p1 ), and idler light (λ ₂ ). By four-wave mixing, converted light (λ ₂ ) that is converted idler light is output from the incident pulse light (λ ₁ ) and adjustment light (λ _p1 ). FIG. 6A is a diagram showing the principle of this wavelength conversion. In the present invention, in the first wavelength conversion, basically the same subscript is attached to the angular velocity corresponding to each wavelength. ω ₂ having an angular velocity shifted from ω _p1 by an angular velocity corresponding to the difference between ω _p1 and ω ₁ is generated. Only the converted light (λ ₂ ) is extracted by the first optical wavelength filter 14 and is incident on the optical delay device 2.

The pulsed light (λ ₂ ) output from the optical delay device 2 has a certain delay amount and is input to the second nonlinear optical element 15 of the second wavelength converter. The second nonlinear optical element 15, together with the pulsed light (lambda _2), the frequency is controlled adjustment light (lambda _p2) is input to convert the wavelength of the pulsed light. In the second nonlinear optical element 15, four-wave mixing is performed using pulsed light and adjustment light. As a result, the second nonlinear optical element 15 outputs three lights of pulsed light (λ ₂ ), adjustment light (λ _p2 ), and idler light (λ ₁ ). By four-wave mixing, converted light (λ ₁ ), which is converted idler light, is output from the pulse light and the adjustment light. FIG. 6B shows the principle of wavelength conversion. Only this converted light (λ ₁ ) is extracted by the second optical wavelength filter 14 and output. The output pulse light (λ ₁ ) is incident on the first wavelength converter 1 having a predetermined delay amount with respect to the remaining light (λ ₁ ) demultiplexed by the demultiplexer 5. Therefore, time-resolved measurement can be performed using the delay controller of the present invention.

  The combination of the first wavelength converter 1 and the second wavelength converter 3 is not limited to these embodiments. For example, the first wavelength converter includes the first wavelength converter according to the first embodiment, that is, the semiconductor optical amplifier 6 and the circulator 7, and the second wavelength converter includes the second wavelength converter according to the second embodiment. The second wavelength converter, that is, the second nonlinear optical element 15 and the second optical wavelength filter 16 may be used.

  FIG. 7 is a block diagram for explaining a basic configuration of an optical delay controller according to an embodiment of the present invention. As shown in FIG. 7, this optical control delay device receives a demultiplexer / multiplexer 20 for demultiplexing and multiplexing light and one light demultiplexed by the demultiplexer / multiplexer 20. A wavelength converter 21, an optical delay device 2 to which light having a wavelength converted by the wavelength converter 21 is input, a first return means 22 for returning output light from the optical delay device 2, Second light returning means 23 for returning the remaining light demultiplexed by the multiplexer 20 toward the demultiplexer / multiplexer 20 is provided.

  The demultiplexer / multiplexer 20 is a device that can demultiplex incident light and can multiplex a plurality of incident lights. The demultiplexer / multiplexer 20 is already known. The demultiplexer / multiplexer 20 can be manufactured by combining, for example, known optical elements. As the optical delay device 2, the one described above can be used as appropriate. As the wavelength converter 21, the same one as the first wavelength converter described above can be used as appropriate. The folding means 22 and 23 are also means for folding the light. An example of the folding means 22 and 23 is a mirror. Since it has such a configuration, the light (first light) that has been demultiplexed by the demultiplexing / multiplexing unit 20 and folded back toward the demultiplexing / multiplexing unit 20 by the second folding unit 23; Light that enters the wavelength converter 21, passes through the optical delay device 2, is turned up by the turn-back means 22, passes through the optical delay device 2 and the wavelength converter 21, and is output to the demultiplexing / multiplexing device 20 2) is multiplexed by the demultiplexer / multiplexer 20. The delay time between these lights (first light and second light) can be controlled.

  Further, unlike the optical control delay device described above, the delay time can be controlled using one wavelength converter, so that the device can be easily controlled, the device can be made compact, and the cost of the device can be reduced.

  This optical delay controller is turned back by the turn-back means 22, and the light output to the wavelength converter 21 through the optical delay device 2 again is returned to the branching / multiplexing unit 20, where the branching / multiplexing unit is returned. 20 is output in the same direction as the remaining light demultiplexed by 20. By doing in this way, the light demultiplexed by the demultiplexer / multiplexer 20 and output first to the target and the light having the same path with a predetermined delay time are output to the target. be able to.

  FIG. 8 is a block diagram for explaining a basic configuration of an optical delay controller according to an embodiment of the present invention. As shown in FIG. 8, the optical delay controller further includes a circulator 25 between the duplexer 5 and the wavelength converter 21. The circulator 25 outputs the incident light toward the wavelength converter 21 when one of the lights demultiplexed by the demultiplexer 5 enters the circulator 25. On the other hand, when the circulator 25 is turned back by the turn-back means 22 and the light output to the wavelength converter 21 through the optical delay device 2 again enters the circulator 25, the circulator 25 outputs the light so as not to return to the wavelength converter 21. The light that has passed through the optical delay device 2 and the circulator 25 is output toward the object.

The present invention can be suitably used in fields such as a spectroscopic analyzer.

The present invention can also be used for generation and detection of electromagnetic waves in the terahertz region (100 GHz to 10 THz) and spectroscopy.

DESCRIPTION OF SYMBOLS 1 1st wavelength converter 2 Optical delay device 3 2nd wavelength converter 4 Optical pulse generator 5 Demultiplexer

Claims (15)

A demultiplexer (5) for demultiplexing pulsed light;
A first wavelength converter (1) on which one of the pulse lights demultiplexed by the demultiplexer (5) is incident;
An optical delay device (2) to which pulsed light whose wavelength has been converted by the first wavelength converter (1) is input;
A second wavelength converter (3) for converting the wavelength of the pulsed light delayed by the optical delay device (2);
Comprising
The optical delay device (2) differs in the amount of delay given to the incident light depending on the wavelength of the incident light. The remaining light demultiplexed by the demultiplexer (5) and the first wavelength converter (1 ) And the delay time between the light output from the optical delay device (2) and the second wavelength converter (3) can be controlled.
Light controlled delay device.
The second wavelength converter (3)
The wavelength of the incident light is changed so that the wavelength of the output light becomes the wavelength of the light incident on the first wavelength converter (1).
The optical control delay device according to claim 1.
An optical pulse generator (4) for generating pulsed light incident on the duplexer (5);
The optical pulse generator (4) includes a mode-locked fiber laser,
The optical control delay device according to claim 1.
An optical pulse generator (4) for generating pulsed light incident on the duplexer (5);
The optical pulse generator (4) includes an optical comb generator,
The optical control delay device according to claim 1.
An optical pulse generator (4) for generating pulsed light incident on the duplexer (5);
The optical pulse generator (4) includes a semiconductor quantum dot comb laser,
The optical control delay device according to claim 1.
The first wavelength converter (1)
It is a wavelength converter using a semiconductor optical amplifier.
The optical control delay device according to claim 1.
The first wavelength converter (1)
Including a semiconductor optical amplifier,
This is a wavelength converter that converts the wavelength of the output light by mixing the adjusting light with the frequency controlled and the incident light.
By controlling the frequency of the adjusting light, the wavelength of the output light is controlled, thereby controlling the delay amount given by the optical delay device (2).
The optical control delay device according to claim 1.
The first wavelength converter (1)
Optical fiber,
The optical control delay device according to claim 1.
The first wavelength converter (1)
It is a wavelength converter that uses semiconductor elements to convert the wavelength of incident light by four-wave mixing.
The optical control delay device according to claim 1.
A first wavelength converter (1);
An optical delay device (2) to which pulsed light having a wavelength converted by the first wavelength converter (1) is input;
A second wavelength converter (3) for converting the wavelength of the pulsed light delayed by the optical delay device (2);
Comprising
The optical delay device (2) differs in the amount of delay given to the incident light depending on the wavelength of the incident light.
Light controlled delay device.
The adjustment light incident on the first wavelength converter (1) and the adjustment light incident on the second wavelength converter (3) in order to convert the wavelength of the pulsed light are the same.
The optical control delay device according to claim 10.
A demultiplexer / multiplexer (20) for demultiplexing and multiplexing pulsed light;
A wavelength converter (21) on which one of the lights demultiplexed by the demultiplexer / multiplexer (20) is incident;
An optical delay device (2) to which pulsed light whose wavelength has been converted by the wavelength converter (21) is input;
First folding means (22) for folding output light from the optical delay device (2);
Second folding means (23) for folding the remaining light demultiplexed by the demultiplexing / multiplexing unit (20) toward the demultiplexing / multiplexing unit (20);
Comprising
The optical delay device (2) differs in the amount of delay given to the incident light depending on the wavelength of the incident light,
The light demultiplexed by the demultiplexer / multiplexer (20) and turned back toward the demultiplexer / multiplexer (20) by the second folding means (23); and the wavelength converter (21) , Through the optical delay device (2), turned back by the turn-back means (22), passed through the optical delay device (2) and the wavelength converter (21), and directed to the branching / multiplexing device (20). The output light is multiplexed in the demultiplexer / multiplexer (20), and the delay time between these lights can be controlled.
Light controlled delay device.
The light that is folded back by the folding means (22) and output to the wavelength converter (21) again through the optical delay device (2) is returned to the demultiplexer (5) and demultiplexed by the demultiplexer (5). Output in the same direction as the remaining wave,
The optical control delay device according to claim 12.
A demultiplexer (5) for demultiplexing pulsed light;
A wavelength converter (21) on which one of the lights demultiplexed by the demultiplexer (5) is incident;
An optical delay device (2) to which pulsed light whose wavelength has been converted by the wavelength converter (21) is input;
A folding means (22) for folding the output light from the optical delay device (2);
Comprising
The optical delay device (2) differs in the amount of delay applied to the incident light depending on the wavelength of the incident light, and the remaining light demultiplexed by the demultiplexer (5); enters the wavelength converter (21). The delay time between the optical delay device (2) and the light reflected by the return device (22) and output to the wavelength converter (21) through the optical delay device (2) can be controlled.
An optically controlled delay device,
A circulator (25) is further provided between the duplexer (5) and the wavelength converter (21);
The circulator (25)
When one light demultiplexed by the demultiplexer (5) is incident on the circulator (25), this incident light is output toward the wavelength converter (21),
When the light which is turned back by the turning means (22) and is output to the wavelength converter (21) again through the optical delay device (2) enters the circulator (25), the light is returned to the wavelength converter (21). Output so that there is no
Light controlled delay device.
  A spectroscopic device comprising the light control delay device according to claim 1.

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