JP2007333753A - Electrooptic ssb optical modulator and optical frequency shifter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrooptic SSB modulator which is driven with low power, and which highly efficiently operates in a high frequency area of 10 GHz or higher even when it has a compact construction, and an optical frequency shifter. <P>SOLUTION: Optical waveguides 2a, 2b are combined with standing wave type resonant electrodes 3a, 3b on an electrooptic crystal board 1 where polarization reversal structures 1a are implemented. The different polarization reversal structures 1a are implemented for the respective optical waveguides 2a, 2b, and the standing wave electric field over the resonant electrodes 3a, 3b is used to perform an optical modulation, thereby obtaining a sine modulation effect and a cosine modulation effect at the same time. Only supplying a single type of modulation signal from a modulation signal source 6 can perform the sine and cosine modulations. The modulation signal is resonated over the resonant electrodes 3a, 3b to obtain a high electric field, whereby an efficient modulation effect can be realized even in a high frequency area higher than 10 GHz. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electro-optic SSB optical modulator and an optical frequency shifter that can be used in an optical communication system, an optical measuring instrument, an optical integrated circuit, an optical instrument, and the like, and more particularly, a quasi-millimeter wave band / millimeter wave band having a frequency of 10 GHz or more. The present invention relates to an electro-optic SSB optical modulator and an optical frequency shifter that can operate with high efficiency.

It is known that an optical signal is modulated with an electric signal by an electro-optic modulator using a ferroelectric material such as LiNbO ₃ (lithium niobate) or LiTaO ₃ (lithium tantalate). However, a technique for freely modulating and controlling a light wave in a high frequency region has not been sufficiently established. For example, a commercially available electro-optic modulator is a DSB (Double SideBand) type modulator that generates a side-by-side frequency component by modulation on both the high-frequency side and the low-frequency side of the frequency of a light wave that is a carrier wave. In this DSB modulation system, there are problems such as redundancy, signal degradation due to wavelength dispersion, and interference between both sideband components. Therefore, for information transmission in optical communication, an SSB (Single SideBand) that generates a sideband frequency component only on one side. ) Type modulation scheme is preferred.

  The SSB modulation method has been used in commercial radio broadcasting for a long time, and its technology has already been established in the radio wave region, but is still in the developing stage in the light wave region. In recent years, in the fields of optical communication using optical waves, optical measurement, and the like, the importance of SSB modulation of optical waves has increased with the advancement of optical wave application technology. For example, in optical communication, an SSB with a small occupied frequency band is used in order to reduce frequency bands per amount of information and effectively use frequency band resources, and to prevent signal degradation due to dispersion of transmission lines such as optical fibers. High-speed optical modulators that operate are regarded as important.

  On the other hand, the optical frequency shifter is important in fields such as optical communication, heterodyne measurement, spectroscopy, and photochemistry. In particular, if an optical frequency shifter operating at several tens of GHz can be used, a plurality of light sources having different frequencies that are essential in a wavelength division multiplexing communication system by several tens of GHz can be easily obtained. Therefore, development of an optical frequency shifter that operates in a high frequency band of several tens of GHz or more is desired.

  As an optical SSB modulator or an optical frequency shifter currently on the market, there is a device using an acousto-optic effect. This device uses light diffraction by sound waves propagating in the crystal, but there is an upper limit to the operating frequency, which is about several hundred MHz. In the high frequency range of 1 GHz or higher, the wavelength of the sound wave becomes smaller than the wavelength of the light wave, and in principle, diffraction does not occur, and the propagation loss of the sound wave in the crystal becomes very large. There is.

  Devices as described below are known as electro-optic SSB optical modulators or optical frequency shifters utilizing the electro-optic effect. This device combines a plurality of light modulation elements and a Mach-Zehnder type interferometer waveguide, applies a modulated signal whose phase is shifted by π / 2 to each light modulation element, and has two light paths. An optical SSB modulation / optical frequency shift action is obtained by giving an optical path difference of λ / 4 to. FIG. 6 is a schematic diagram of this conventional electro-optic SSB optical modulator or optical frequency shifter.

In FIG. 6, a first optical waveguide 61 provided with a high-frequency phase modulator 51 to which a modulation signal sin (2πf _m t) is applied, a low-frequency phase modulator 52 to which a DC signal is applied, and a modulation signal cos. A high frequency phase modulator 53 to which (2πf _m t) is applied is arranged in parallel with a second optical waveguide 62 provided in series. The axis orthogonal to the complex plane (Re-Im) indicating the phase indicates the frequency (ν).

  As shown in FIG. 6, the light wave input is divided into two parts, a first optical waveguide 61 and a second optical waveguide 62, and each is phase-modulated using a modulation signal whose phase is shifted by π / 2, Further, by synthesizing these two light waves after shifting the phase by π / 2 (λ / 4), one sideband component is canceled, and an optical SSB modulation action is obtained. At this time, by appropriately selecting the depth of the phase modulation, it is possible to suppress only the frequency component of the transported light wave and extract only the SSB primary sideband component, and function as an optical frequency shifter.

  The circuit configuration shown in FIG. 6 is also used in an SSB modulator in the radio wave region. Many of the electro-optic SSB optical modulators or optical frequency shifters proposed so far are shown in FIG. A plurality of such electro-optic phase modulators and Mach-Zehnder type optical waveguides are combined. Since this system uses the electro-optic effect, high-speed operation can be expected in principle. However, it is necessary to prepare two types of signals whose phases are shifted by π / 2 as modulation signals. There is a problem that there is.

  In addition, although a method of combining a normal DSB modulator and a narrow-band bandpass optical filter is also conceivable, there are problems such as a complicated system configuration and difficulty in configuring a narrow-band filter circuit in the optical region, It's not a realistic method.

  There is also an SSB modulation method that uses two clockwise and counterclockwise circularly polarized lights, but it is difficult to make a waveguide and a large amplitude modulation signal must be used. There are problems such as increase, and it cannot be said that it is a practical method.

  Furthermore, an optical frequency shifter using an oblique periodic polarization reversal structure has been proposed (see Patent Document 1). This is similar to the present invention in that it uses an electro-optic effect and uses a domain-inverted structure (domain-inverted structure). A phase grating is to be obtained, and the essential operation principle is different from that of the present invention described later. This device is also difficult to be made into a waveguide and has problems such as compatibility with an optical fiber communication system and an increase in operating power.

Therefore, the present inventor has proposed a periodic domain inversion structure electro-optic SSB optical modulator / optical frequency shifter that can operate in a high frequency range of 1 GHz or more by skillfully utilizing the polarization inversion structure (domain inversion structure). (See Patent Document 2). This device uses an electro-optic crystal having a periodically poled structure in which the spatial arrangement is shifted from one another by a quarter period, and the electro-optic crystal is combined with a Mach-Zehnder interferometer waveguide and traveling wave electrode. A sin modulation action and a cos modulation action can be achieved simply by supplying a modulated wave from one power supply circuit.
Japanese Patent No. 2802366 JP 2002-62516 A

  In the device described in Patent Document 2, optical SSB modulation characteristics can be obtained with low power in a frequency range of about 1 to 10 GHz with a simple configuration. However, when the frequency becomes a quasi-millimeter wave band / millimeter wave band exceeding 10 GHz, there is a problem to be improved that efficiency is lowered due to an increase in loss due to an electrical signal flowing only on the surface of the electrode. There is a need to develop a device capable of efficiently performing optical SSB modulation even in the quasi-millimeter wave band and the millimeter wave band.

  The present invention has been made in view of such circumstances, and can be driven with low power, and can operate with high efficiency in a high-frequency region of 10 GHz or more, and an optical device that can be driven with low power and a small configuration. An object is to provide a frequency shifter.

  The electro-optic SSB optical modulator according to the present invention has a configuration in which an optical waveguide and a standing-wave electrode are combined with an electro-optic medium partially having a domain-inverted structure, and a standing wave at the electrode. The light wave traveling through the optical waveguide is modulated using an electric field.

  The electro-optic SSB optical modulator according to the present invention is characterized in that, in the above configuration, the number of the optical waveguides is two, and the pattern of the polarization inversion structure in each optical waveguide is different.

  The electro-optic SSB optical modulator according to the present invention is characterized in that, in the above configuration, the electrode is a resonant electrode.

  The optical frequency shifter according to the present invention has a configuration in which an optical waveguide and a standing wave type electrode are combined with an electro-optic medium having a partially domain-inverted structure, and a standing wave electric field at the electrode is used. Thus, the frequency of the light wave traveling through the optical waveguide is shifted.

  The electro-optic SSB optical modulator of the present invention has a configuration in which an electro-optic medium having a polarization inversion structure at a desired position is combined with an optical waveguide and a standing wave type electrode. In two optical paths of an optical waveguide (for example, a Mach-Zehnder interferometer waveguide), by applying different polarization inversion structures and performing optical modulation using a standing wave electric field on the same electrode, sin modulation action and cos The modulation effect can be obtained simultaneously. For this reason, sin modulation and cos modulation can be performed only by supplying one type of modulation signal from the power feeding circuit. By using the modulation phase control characteristic in a structure in which a standing wave type electrode and a polarization inversion structure are appropriately combined, an optical modulation circuit equivalent to that shown in FIG. 6 is realized using only an optical waveguide and a standing wave type electrode. . In addition, since a resonant electrode is used as the standing wave electrode, a high electric field can be obtained by resonating the modulation signal on the electrode, and an efficient modulation action can be obtained even in a high frequency range of 10 GHz or higher.

  In the optical frequency shifter of the present invention, the power of the modulation signal supplied in the electro-optic SSB optical modulator described above is increased to control the phase modulation depth deeply, thereby shifting the carrier light component (frequency shift). The conversion efficiency from the non-component) to the sideband component (frequency shifted component) is increased, and the carrier light component is reduced so that the sideband component becomes dominant.

  In the present invention, an electro-optic medium having a domain-inverted structure is combined with an optical waveguide and a standing wave type electrode, and a standing wave electric field on the electrode is used to modulate a light wave traveling through the optical waveguide. Since the optical SSB modulation with high efficiency can be performed even in the high frequency region, the electro-optic SSB optical modulator and the light that operate with high efficiency even in the millimeter wave band frequency of 10 GHz or more, particularly exceeding 30 GHz. A frequency shifter can be realized.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. FIG. 1 is a configuration diagram of an electro-optic SSB optical modulator 10 of the present invention. In FIG, 1 is a ferroelectric material (e.g., z-cut LiNbO ₃ or z-cut LiTaO ₃₎ tabular electrooptic crystal substrate made (hereinafter, simply referred to as a substrate). One Mach-Zehnder interferometer waveguide 2 as an optical waveguide is formed on the surface of the substrate 1.

  Each of the upper portions of the two optical waveguides 2a and 2b (thick line portions in FIG. 1) constituting the Mach-Zehnder interferometer waveguide 2 is a good conductor metal (for example, aluminum or gold) that resonates at a designed modulation frequency. Resonant electrodes 3a and 3b are provided. As the high-frequency line constituting the resonance electrodes 3a and 3b, a symmetric coplanar line, a microstrip line parallel coupled line, or the like can be used. The end of the line may be opened or short-circuited as shown in FIG. A power supply 4 for power supply extends from the middle of one resonance electrode 3b, and a modulation signal source 6 and a variable DC voltage source are connected between the power supply 4 for power supply and a ground electrode 5 provided on the back surface of the substrate 1. Seven series circuits are provided.

  The resonance electrodes 3a and 3b can resonate by receiving a modulation signal from the outside and generating a standing wave. Then, a refractive index change is generated in the substrate 1 by the electric field of the resonance standing wave of the modulation signal generated in the resonance electrodes 3a and 3b, and an optical modulation action is obtained. The line lengths of the resonant electrodes 3a and 3b are about several times the wavelength of the standing wave. The shape of the resonant electrodes 3a and 3b may be arbitrary as long as standing waves are generated.

  A desired region of the substrate 1 corresponding to the two optical waveguides 2a and 2b is provided with a domain-inverted structure 1a (the hatched portion in FIG. 1). The arrows in FIG. 1 indicate the direction of spontaneous polarization in the substrate 1. The polarization reversal structure 1a is applied to compensate for the travel time effect described later. By adjusting the reversal pattern in advance in both the optical waveguides 2a and 2b, the polarization reversal structure 1a in each of the waveguides 2a and 2b. The modulation phase of the high-frequency phase modulation is shifted by π / 2 to obtain a sin modulation action and a cos modulation action necessary for optical SSB modulation.

  In the configuration described above, a direct current voltage for giving an optical path difference (optical bias) of π / 2 (λ / 4) between the two waveguides 2a and 2b is superimposed on the high frequency modulation signal and applied to the resonance electrode 3b. However, a bias electrode having an appropriate length may be separately provided to apply a DC voltage. Further, a static optical path difference (optical path phase shift) may be given between the two optical waveguides 2a and 2b. Furthermore, although the resonance electrodes 3a and 3b are directly provided on the substrate 1, a buffer layer may be interposed in order to reduce the light wave propagation loss.

  Next, the control principle of the modulation phase in the present invention will be described with reference to FIGS. Consider an electro-optic modulator 20 as shown in FIG. 2A in which a resonant modulation electrode 13 to which a high-frequency modulation signal is applied is provided on an optical waveguide 12 of an electro-optic crystal substrate 11. The electro-optic modulator 20 uses the resonance type modulation electrode 13 as a resonance circuit for the modulation signal, and resonates the modulation signal on the resonance type modulation electrode 13 to obtain a high electric field. As a result, an efficient modulation action can be obtained even in a high frequency range.

  When the length of the resonance electrode is increased (integer multiple of the wavelength of the modulation signal), it is necessary to consider the influence of the travel time of the light wave (travel time effect). Since the propagation speed of the light wave in the medium is very fast, normally, when modulating the light wave at a low frequency (1 MHz or less), the modulated signal in the time required for the light wave to pass through the modulator (light wave travel time) The change in time is negligibly small. However, when the modulation signal becomes a high frequency region, the change of the modulation signal within the traveling time of the light wave cannot be ignored. Therefore, in the present invention, the travel time effect is compensated by applying the domain-inverted structure 1 a to a desired position of the electro-optic crystal substrate 1. The principle of this compensation will be described in detail below.

In FIG. 2A, the time when the light wave reaches the optical waveguide 12 immediately below the left end (point A) of the resonance type modulation electrode 13 of the electro-optic modulator 20 is t _A , and the resonance type modulation electrode at time t _B. It is assumed that the light wave reaches a position (point B) of ¼ from the left end of 13. Since the resonant modulation electrode 13 has a resonant line structure in which a standing wave stands along the light wave propagation direction, the modulated electrical signal is a standing wave, and the modulated wave does not move on the line. Instead, the voltage at each point on the resonant modulation electrode 13 vibrates with time (see FIG. 2B).

Since the voltage on the resonant modulating electrode 13 between the light waves traveling time (t _B -t _A) varies, depending on the relationship between the electrode length and the light wave velocity, as shown in FIG. 2 (c), the light waves When the point B is reached, the polarity of the modulated wave electric field seen by the light wave is reversed. Under such circumstances, after time t _B , the light wave propagates in the modulated wave electric field having the opposite sign to the electric field seen between AB on the resonant modulation electrode 13, so that it has accumulated so far. The total modulation effect is reduced by receiving the modulation opposite to the modulation effect received in step (b). Depending on the conditions, a situation occurs in which the modulation component is finally canceled at a certain point (x = 0). This is the travel time effect.

  In order to compensate for this transit time effect, the present invention utilizes a domain-inverted structure. In a region where the modulation action is canceled due to the travel time effect, by reversing the polarization direction of the electro-optic crystal substrate 11 in advance, the modulation sign in this region is reversed, and the modulation effect due to the travel time effect is reduced. The decrease can be compensated for and a cumulative modulation effect can be obtained (FIG. 2 (d)).

  The region where the polarization is reversed can be determined by the group velocity of the light wave, the electrode length, the wavelength and frequency of the modulated standing wave, and the time when the light wave serving as a time reference is incident on the electrode end. In an electro-optic modulator having a resonant electrode structure that resonates at a certain modulation frequency, the region where polarization inversion is to be performed includes the wavelength of the standing wave on the electrode, the distance that the light wave travels within the half period of the modulation signal, the light wave Is determined by the relationship with the phase of the modulation signal when it enters the electrode end (point A in FIG. 3A). That is, even with a modulator having the same structure, the polarization inversion changes according to the phase of the modulation signal when the light wave is incident.

As an example, consider the case where the modulation signal is a single frequency sinusoidal signal. The line length is set to two standing waves on the line, and both ends of the line are short-circuited. Further, the distance traveled by the light wave during a half-cycle time of the modulation signal (T / 2, T is one cycle of the modulation signal) is defined as one standing wave wavelength on the line. This corresponds to the case of a modulator having a standard structure using lithium tantalate (LiTaO ₃ ). At this time, it is assumed that the modulation signal has the maximum phase between AB at time t _A1 when the light wave is incident on the electrode end A point. The modulated wave electric field seen by the light wave that enters the electrode end A point at time t _A1 and propagates through the modulator is as shown in FIG. In consideration of reversing the direction of spontaneous polarization in the region where the polarity of the electric signal is reversed due to the travel time effect, the polarization reversal pattern may be as shown in FIG. On the other hand, at the time t _A2 when the light wave is incident on the electrode end A, when the phase relationship is zero (t _A2 = t _A1 + T / 4) on the electrode between AB, the light propagates through the modulator. Since the modulated electric signal seen by the light wave is as shown in FIG. 3D, the corresponding polarization inversion pattern may be as shown in FIG.

  The magnitude of the modulation effect obtained is almost the same when the polarization inversion pattern of FIG. 3C is applied and when the polarization inversion pattern of FIG. 3E is applied. When the traveling distance of the light wave at the half-cycle time (T / 2) of the modulation signal is exactly equal to one standing wave wavelength on the line, the magnitudes of both modulation actions are completely the same. FIG. 3C and FIG. 3E show even and odd symmetric polarization inversion patterns with respect to the center, respectively.

  For this reason, when the distribution of the modulated wave electric field seen by the light wave is an even function distribution (FIG. 3B), the modulation effect increases when the polarization inversion pattern of FIG. When the polarization inversion pattern e) is applied, the modulation effects cancel each other and the modulation action becomes zero. On the other hand, when the modulation wave electric field distribution seen by the light wave is an odd function distribution (FIG. 3 (d)), the modulation effect is increased when the polarization inversion pattern of FIG. 3 (e) is applied. Similarly, when the polarization inversion pattern is applied, the modulation action becomes zero. That is, in FIG. 3 (c) and FIG. 3 (e), the magnitude of the modulation effect obtained when driven by the same modulation signal is the same, but the phase of the modulation effect is shifted by 1/4 period. Become. Therefore, a modulation action by a sine wave and a modulation action by a cosine wave are obtained.

  FIGS. 4A to 4E are diagrams showing changes with respect to the incident time of a modulated wave electric field seen by a light wave. In each incident time, a polarization inversion pattern can be applied so as to increase the modulation effect, and the travel time effect can be compensated.

  As described above, the feature of the present invention is that by adjusting the polarization inversion structure applied to the electro-optic medium, the incident time of the light wave that can obtain the optimum modulation action is changed, that is, the phase is shifted. It is to obtain the modulation effect. Since the polarization inversion structure is used for controlling the modulation phase, the modulation wave only needs to be in phase (or opposite phase), and a complicated power supply circuit is not required. Also, the device structure is a push-pull type modulator configuration consisting of one Mach-Zehnder interferometer waveguide and one resonant electrode, and is very small and simple. Furthermore, since the optical modulation by the resonance type electrode is used as the operating principle, a very efficient modulation action can be obtained even in the high frequency region.

  In this way, according to the present invention, a small and highly efficient high-speed electro-optic SSB optical modulator that operates in the millimeter band can be realized without using a complicated high-frequency power feeding circuit as shown in FIG.

  Next, a specific example of the electro-optic SSB optical modulator of the present invention will be described while describing its manufacturing process and evaluation characteristics. FIG. 5 is a diagram showing the procedure of the manufacturing process of the electro-optic SSB optical modulator. In the following example, a case will be described in which the operating frequency is 15 GHz and a light wave having a wavelength of 1.3 to 1.5 μm used in the optical communication system is modulated.

Z-cut LiTaO ₃ was used for the electro-optic crystal that becomes the substrate 1 (length: 40 to 45 mm, width: 8 mm, thickness: 0.4 mm). First, a pulse voltage (amplitude: 8.8 kV, period: 10 ms) is selectively applied to a desired portion on the substrate 1 to form a polarization inversion structure 1a (hatched portion) (FIG. 5). (A)).

  Next, a Mach-Zehnder interferometer waveguide 2 was formed on the surface of the substrate 1 provided with the domain-inverted structure 1a by a benzoic acid proton exchange method (proton exchange conditions: 240 ° C., 12 hours) (FIG. 5B). Each optical waveguide 2a, 2b has a width of about 4 μm and a depth of about 1.5 μm.

Next, an SiO ₂ buffer layer (thickness: 0.1 μm) is formed over the entire surface of the substrate 1, and aluminum resonant electrodes 3a and 3b are formed on the optical waveguides 2a and 2b. A working electrode 4 was prepared, and a ground electrode 5 was formed on the back surface of the substrate 1 (FIGS. 5C and 5D). The lengths of the resonance electrodes 3a and 3b were set to 8.6 mm so as to be twice the wavelength of the standing wave at the designed operating frequency of 15 GHz (fourth harmonic resonance length). The width of the resonant electrodes 3a and 3b was 50 μm, the thickness was 2 μm, and the distance between the resonant electrodes 3a and 3b was 30 μm. After these electrodes were fabricated, thermal annealing (400 ° C., 1 hour) was performed to compensate for deterioration of the electro-optic effect due to proton exchange.

  An operation experiment was performed using the electro-optic SSB light modulator manufactured as described above. Laser light (wavelength: 1.3 μm) emitted from the YAG laser was used as a light wave. As designed, it was confirmed that the resonant electrodes 3a and 3b exhibit a fourth harmonic resonance characteristic at an operating frequency of 15 GHz.

  In addition, as a result of the modulation experiment, it was confirmed that the optical SSB modulation characteristic was good in the 15 GHz band. The extinction ratio between the sidebands was 15 dB or more, and the 3 dB band was 1 GHz or more. When the modulation efficiency was measured, a phase modulation depth (phase modulation index) of 0.3 rad was obtained for a driving power of 100 mW. Furthermore, if the device manufacturing conditions are improved, it is possible to obtain a phase modulation depth of 1 rad or more at a driving power of 100 mW.

  From the above results, even when the modulation frequency is 40 GHz, for example, it is possible to obtain a phase modulation depth of 1 rad or more at a driving power of 100 mW by setting the electrode length to about 15 mm. In the electro-optic SSB optical modulator disclosed in Patent Document 2, only a phase modulation depth of about 0.1 rad can be obtained for a modulation frequency of 40 GHz and an electrode length of 30 mm.

  Finally, the optical frequency shifter of the present invention will be described. The basic configuration of the optical frequency shifter is the same as the configuration of the electro-optic SSB optical modulator described above (see FIG. 1). In the configuration of FIG. 1, when the power of the modulation signal source 6 is increased to increase the phase modulation depth, the conversion efficiency from the carrier light component to the modulation sideband component increases. Specifically, when the phase modulation depth is about 2 rad, the frequency of the carrier light is about 5% of the modulated light sideband component, and only the modulated primary sideband component on one side is suppressed by suppressing the carrier light component. It is possible to take it out.

  As a result, the frequency of light can be shifted, and the configuration of FIG. 1 functions as an optical frequency shifter. If the modulation depth is kept constant and the frequency of the modulation signal is swept temporally, the frequency of the output light can be swept temporally (changed continuously).

It is a block diagram of the electro-optic SSB optical modulator or optical frequency shifter of the present invention. It is a figure which shows the relationship between the modulation wave electric field on a resonance electrode, and the modulation wave electric field which the light wave which passes through the modulator sees. It is a figure which shows the relationship between the spatial arrangement | positioning of a polarization inversion pattern, and a modulation phase. It is a figure which shows the change with respect to the incident time of the modulated wave electric field which a light wave sees. It is a figure which shows the procedure of the manufacturing process of an electro-optic SSB light modulator. It is a schematic diagram of a conventional electro-optic SSB optical modulator or optical frequency shifter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electro-optic crystal substrate 1a Polarization inversion structure 2 Mach-Zehnder interferometer waveguide 2a, 2b Optical waveguide 3a, 3b Resonant electrode 4 Feeding electrode 6 Modulation signal source 7 Variable DC voltage source 10 Electro-optic SSB optical modulator

Claims (4)

  Modulation of light waves traveling in the optical waveguide using a standing wave electric field at the electrodes, with a configuration in which an optical waveguide and a standing wave electrode are combined in an electro-optic medium with a partially domain-inverted structure An electro-optic SSB light modulator characterized in that   2. The electro-optic SSB optical modulator according to claim 1, wherein the number of the optical waveguides is two, and the pattern of the polarization inversion structure in each optical waveguide is different.   3. The electro-optic SSB light modulator according to claim 1, wherein the electrode is a resonant electrode. A frequency of a light wave that travels through the optical waveguide using a standing wave electric field at the electrode having a configuration in which an optical waveguide and a standing wave type electrode are combined in an electro-optic medium that is partially polarized. An optical frequency shifter characterized by shifting the frequency.

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