JPH0640596B2 - Semiconductor laser wavelength conversion method and conversion device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor laser wavelength conversion method and conversion device capable of realizing functions such as a multi-wavelength light source, optical pulse width control, optical pulse punching, and optical logic. And is applied to the fields of optical communication, optical switching, optical information processing, and optical computers.

(Problems to be Solved by Prior Art and Invention) As is well known, a semiconductor laser is usually used as a light source for oscillating light, but it can be used as an optical amplifier depending on driving conditions. The optical amplification operation in a region where the signal light power is large has an essentially non-linear effect, and also has a function as a wavelength conversion device for converting the wavelength of light, for example.

In such a wavelength conversion device based on the optical amplification function of a semiconductor laser, a weak probe light (frequency: f ₀ + δf) is conventionally incident in the vicinity of the oscillation frequency f ₀ of a normal semiconductor laser. Alternatively, an optical amplifier biased below the oscillation threshold of an ordinary semiconductor laser is provided with a strong pump light matched to its gain resonance frequency f ₀ and a weak probe light slightly deviated in frequency (+ δf of frequency f ₀ ). ), Two strong pump lights that travel in opposite directions at the same frequency f ₀ are used in an optical amplifier with a traveling waveform in which antireflection films are applied to both end faces of a semiconductor laser. There is a configuration in which three light waves of weak probe light (frequency: + δf of frequency f ₀ ) that travels in the same direction and have slightly different frequencies are made incident, and both of them are amplified output of the input light and f ₀ of the input light. It has been reported that signal light wavelength-converted to a frequency of −δf can be obtained (H. Nakajima and R. Frey: Appl. Phys. Lett., Vo
l.47, pp. 769 (1985), H. Nakajima and R. Frey: Phy
s. Rev. Lett., Vol. 54, pp. 1798 (1985), and G. Agr.
awal: Opt. Lett., Vol.12, No.4, pp.260 (1987)).

However, the conventional device uses a normal semiconductor laser with a reflectivity of about 30% on both end faces, and its optical amplification is essentially a resonance type amplifier operation using multiple reflections between both end faces. Therefore, a large amplification gain was obtained only within a narrow band of about 1 GHz near the longitudinal mode wavelengths (resonance frequency f ₀ ) scattered at about 100 GHz intervals. As a result, the wavelength range in which the wavelength conversion operation can be performed is limited to the vicinity of the longitudinal mode wavelength, and the wavelength conversion efficiency sharply decreases as the detuning frequency | δf | between the pump light and the probe light increases (for example, , Δf = ± 1 GHz, about 1/10). Further, in order to operate it stably, frequency tuning for adjusting the frequency of the input light within the narrow gain band described above is indispensable, and it is necessary to control the temperature and current of the light source and the wavelength conversion device with high accuracy. was there. Further, since the conventional device performs the resonance-type amplification operation, even if the optical input is from one direction, there is light that travels in both directions inside the resonator, and the nonlinearity between the light waves that travel in mutually opposite directions is present. Wavelength-converted light was generated by the interaction, and the same optical output existed in both the output side and the input side. This means that when this wavelength conversion device is connected and operated in multiple stages, only half of the wavelength-converted signal light can be used as an input to the next stage. There was also a problem in terms of efficiency and configuration, such as the need to use an optical isolator between each stage in order to eliminate the re-injection of the input light and the signal light from the above equipment to the previous equipment. .

Further, in the conventional apparatus, three input lights, that is, two pump lights of the same frequency traveling in opposite directions and a probe light of a slightly different frequency from this are required, and the wavelength conversion output is the traveling direction of the probe input light. However, there are major drawbacks in terms of complexity of configuration and difficulty in use as a wavelength conversion device, such as being obtained only in the opposite direction.

(Object of the invention) The present invention has been proposed in order to improve the above-mentioned drawbacks, and its object is to set an operating wavelength arbitrarily within a gain width and to provide a wavelength conversion efficiency in a wide band of several GHz or more. The signal light, which is almost flat across the entire wavelength range and is wavelength-converted by the non-linear interaction of the two input light waves traveling in the same direction, can be obtained only in the same traveling direction as the input light, and highly accurate temperature control and injection current control can be performed for the operation. An object of the present invention is to provide a semiconductor laser wavelength conversion method and a conversion device which are not necessary.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an optical amplifier having an antireflective film on the optical resonator surface of a semiconductor laser, in which the polarization planes of the two are not orthogonal to each other. A semiconductor laser wavelength conversion method is characterized in that two light waves having different frequencies are input in the same direction to extract output light whose wavelength is converted in the traveling direction of the input light.

Further, the present invention provides a semiconductor laser wavelength conversion device characterized by comprising a semiconductor optical amplifier having an antireflective film on the optical resonator surface of a semiconductor laser having a current injection terminal, and an optical multiplexer on its input side. It is the gist of the invention.

The difference between the features of the present invention and the conventional technique is as follows.

The present invention, by applying an antireflection film on both end surfaces of the semiconductor laser,
In a traveling waveform laser amplifier with end face reflectivity of 0.1% or less, set the injection current within the range where a large signal gain can be obtained with a single pass, and then match the polarization planes of the two light waves of the pump and probe with different frequencies. The most main feature is that the output light is obtained in the same direction as the traveling direction of the input light by inputting in the same direction.

However, in the conventional technique, as described above, the operation is essentially based on the non-linear interaction between the three light waves of the two pump lights and the probe light traveling in opposite directions. Thus, output light in both the same direction and the opposite direction, or output light in only the opposite direction is obtained. On the other hand, in the present invention, the unidirectional amplification process with respect to the input light and the nonlinear interaction based on the phase matching between the two light waves traveling in the same direction are used to output the output light only in the same direction as the traveling direction of the input light. The obtained structure is significantly different from the conventional technique.

Next, examples of the present invention will be described. In addition, the embodiment is one exemplification, without departing from the spirit of the present invention,
It goes without saying that various changes or improvements can be made.

(Embodiment) FIG. 1 (a) is a diagram for explaining the first embodiment of the present invention, in which 11 is a semiconductor laser, 12 is an active layer waveguide for carrier confinement and optical confinement, Reference numerals 13 and 14 denote current injection terminals for the semiconductor laser 11. Reference numeral 15 is an antireflection film formed on the end face of the semiconductor laser, and is designed so that the residual reflectance with respect to the waveguide mode propagating in the waveguide is 0.1% or less.

To operate this, first, a direct current is applied between 13 and 14 in the forward direction with respect to the pn junction of the semiconductor laser 11. At this time, the injection current is increased from the original oscillation threshold current of the semiconductor laser 11 before forming the antireflection film 15,
Set the signal gain at the gain peak wavelength to about 20 dB or more (Fig. 1 (d)). Then, as the input light 17, two light waves of the pump and the probe, which are aligned on the same optical axis by the multiplexer 16 and have different frequencies, are polarized in parallel with the active layer surface of the semiconductor laser. State (TE
Polarization), when input in the same traveling direction, output light 18 is extracted in the transmission direction. FIGS. 1 (b) and (c) schematically show the spectra of the input light 17 and the output light 18, respectively. The input light is strong pump light E _0in (f ₀ ) and weak probe light E _1in (f ₀
In contrast to the two waves of + δf), the output light has a frequency of f ₀ −δf in addition to the amplified pump light and probe light outputs E ₀ (f ₀ ) and E ₁ (f ₀ + δf). New signal electric field E ₂ (f ₀ −
δf) is included.

FIG. 2 shows the spectrum of the output light observed by using the Fabry-Perot spectrum analyzer, in which the experiment was conducted according to the above-mentioned configuration and operation method. In the experiment, a 1.5 μm band InGaAsP traveling waveform laser amplifier whose residual reflectance was reduced to 0.03% by an antireflection film was biased to 80 mA, which is 2.3 times the original and oscillation threshold, and the unsaturated signal gain was 19 dB. Used in the state. FIGS. 2 (a) and 2 (b) are output light spectra when the CW pump light and the probe light are individually input to the amplifier. The input power of pump light and probe light is 87 each.
It is set to μW and 23 μW, and the polarization planes of both waves match the TE wave of the amplifier. At this time, the amplification gains for the independent pump light and probe light are 17 dB and 18 dB, respectively.
It has changed to dB, which means that this traveling waveform laser amplifier is operating in the gain saturation region (non-linear region). FIG. 2 (c) to (g) show output light spectra when pump light and probe light are simultaneously incident. Here, the pump light wavelength is fixed at 1.515 μm, and only the probe light wavelength is changed while keeping the input light power constant. Fig. 2 (c)
~ (E) is the detuning frequency δf of the probe light to the pump light
Is negative, and (f) and (g) are results when δf is positive. Regardless of whether the probe light detuning is positive or negative, a wavelength-converted signal light of about 0.5 mW is obtained. . At this time,
The wavelength conversion efficiency or wavelength conversion gain, which is defined as the ratio of the wavelength converted signal light output to the probe input light power, is about 13 dB, and very highly efficient wavelength conversion operation is realized. FIG. 3 is a plot of the pump light, probe light, and signal light outputs obtained in this experiment as a function of detuning δf of the probe light with respect to the pump light, and the wavelength-converted signal light power is ± 1.5. It shows a nearly flat dependence on detuning up to GHz.

The generation mechanism of this new signal light electric field E ₂ (f ₀ −δf) is the non-degeneracy based on the third-order optical nonlinear interaction between the pump light E ₀ and the probe light E ₁ amplified in the semiconductor gain medium. It is analyzed as a four-wave mixing process, and its elementary process is expressed by E ₂ = χ ⁽³⁾ E ₀ E ₁ ^* E ₀ . (However, χ ⁽³⁾ third-order nonlinear optical constant, E ₁ ^*
Represents the multiple conjugate electric field of E ₁ . ) That is, due to the optical mixing between E ₀ and E ₁ ^* , the injected carrier density in the active layer is modulated by the beat frequency component δf of both, and the resulting dynamic diffraction grating of carrier density diffracts the pump light E _0. Has been
A new signal light E ₂ (f ₀ −Δf) is generated. Therefore, the efficiency of this wavelength conversion is proportional to | E ₀ E ₁ | cos (θ), where θ is the angle formed by the polarization planes of E ₀ and E ₁ ^*. The most effective method is to make the input coincide with each other (θ = 0). Further, the signal light E ₂ generated by this four-wave mixing is proportional to E ₁ ^*, and is therefore also called a phase conjugate wave of the probe light E ₁ .

Next, the influence of the amplification gain profile in this wavelength conversion process will be described. By providing the antireflection film 15, the semiconductor laser 11 operates as a traveling waveform laser amplifier, and its amplified signal gain spectrum is 9000 as shown in FIG. 1 (d).
Has a gentle characteristic over a wide band of GHz. Therefore,
No matter where the pump light frequency is set within this gain band, wavelength-converted output light can be obtained as long as the detuning of the probe light is within the range of several GHz. Does not require control. Also,
The detuning characteristic of the wavelength-converted optical output is that the period of fluctuation of the injected carrier density induced by the optical mixing between E ₀ and E ₁ ^* becomes shorter than the carrier lifetime τ _S which is the response time of the injected carrier. The limitation due to the narrow band property of the amplification gain, which was more dominant in the resonance type laser amplifier of the conventional device, is eliminated only by the effect of reducing this fluctuation component. Further, since the traveling-wave laser amplifier operates at a larger current value than that of the resonance type laser amplifier, the carrier lifetime value is reduced to 1/5 of that of the conventional device. Due to both of these effects, the device has a wavelength Wideband detuning operation in conversion is possible. The solid line, the one-dot chain line, and the broken line in FIG. 3 show theoretical values for the wavelength-converted signal light, the probe light, and the pump light, respectively, with respect to τ _S = 0.2 ns in the apparatus of this embodiment.

Further, in the gain spectrum of FIG. 1 (d), no remarkable resonance peak at the longitudinal mode wavelength appears, and the semiconductor laser 11
This means that the present device, which is composed of the antireflection film 15 and the antireflection film 15, operates as a traveling waveform laser amplifier that obtains a signal gain by passing the incident light only once. Therefore, when pump light and probe light are input in the same direction as in this embodiment,
There is no light that goes back to the input side due to the reflection from the output side end face. Furthermore, the elementary process that produces the wavelength converted signal light is E ₂ =
χ ⁽³⁾ E ₀ E ₁ ^* E ₀ , so k for that wave vector
_{2 = 2k 0 -k 1 ≒ k} 0 of the signal light traveling in the same direction as the input pump light from the phase matching condition E ₂ only permitted. Thus, by the combination of the unidirectional amplification process and the phase matching condition,
In principle, the output light is configured and operated so that it is output only in the same direction as the traveling direction of the input light. Although 0.1% was shown as a guideline for the residual reflectance of both end faces, the requirement therefor strongly depends on the magnitude of the gain controlled by the amount of current injected into the optical amplifier. To do. The degree of unidirectional amplification can be evaluated as the magnitude of (modulation) in the wave of the gain (shown by the broken line in FIG. 1 (d)) due to the resonance effect appearing in the gain spectrum of FIG. 1 (d), The ratio of this wave to the valley peak (if u '/ u in Fig. 1 (d) is allowed up to 0.5, 2.4%, 0.25%, and 10% for signal gains of 10, 20 and 30 dB, respectively. The reflectance must be 0.025% or less. (At this time, the magnitude of the single pass gain is
These are 8.5, 18.5, and 28.5 dB. If the reflectance becomes smaller than the above value, the valley-to-peak ratio approaches 1, and a higher-performance traveling-wave optical amplifier and more complete unidirectional amplification can be obtained. Thus, it is necessary to reduce the reflectance as the gain is increased. The wavelength conversion operation described in the present embodiment can be realized in the low gain region, but the output is large and the effect is large as it is operated in the high gain region. Therefore, the reflectance value is preferably set to 0.1 to 0.01%. It should be noted that, in addition to the configuration in which the reflectances on both end surfaces are both set to 0 as described above, the input side reflectance and 0 at any value other than 0 or 1 are used.
Even with the configuration having the output side reflectance of 1, the unidirectional amplification with respect to the input / output light is ensured, and thus it is clear that the wavelength conversion operation similar to that of the present embodiment can be realized. Although the basic operation in the case of inputting two light waves of different wavelengths has been described in detail in the present embodiment, the number of input wavelengths is not limited to two, and the same wavelength conversion is applied to a plurality of input light of two or more different wavelengths. It is possible to operate. In this case, the wavelength-converted light is generated by the non-linear interaction between any two light waves, so it is necessary to consider the arrangement in which the frequency intervals of the respective input lights are shifted from the equal intervals.

As is clear from the results obtained so far, there have been great improvements in comparison with the prior art in terms of expanding the operating wavelength range, broadening the wavelength conversion characteristics, stabilizing the operation, and simplifying the configuration. In addition, this device is characterized in that the output light has an amplification gain of about 13 to 18 dB with respect to the input light at the same time as performing the wavelength conversion, and is different from other devices as will be described later in other embodiments. Even when used in combination, there is an advantage that the insertion loss can be compensated. In the above experimental example, CW light was used for both the pump light and the probe light, but since E ₂ is proportional to E ₁ ^* , even if the probe light E ₁ is intensity-modulated light or frequency-modulated light, The wavelength of the replica of the optical spectrum is converted to a position whose center frequency is shifted by 2δf. Therefore, if the modulated light for signal transmission is used as the probe light and is input together with the CW pump light, it can also be used as a wavelength conversion optical amplification repeater for optical transmission.

FIG. 4 is a diagram of an input / output optical spectrum for explaining the second embodiment of the present invention, in which (a) shows the input optical spectrum and (b) shows the output optical spectrum. Although the same configuration is used, the feature is that the intensities of the input pump light and the probe light are set to be substantially equal. Also act as E _0in the probe light at the same time acts as a pump light E _1in in this case, E ₂
＝ χ ⁽³⁾ E ₀ E ₁ ^* E ₀ occurs in the elementary process of E ₂ (f ₀ −δf), and at the same time E ₃ = χ ⁽³⁾ E ₁ E ₀ ^* E _{1 in} the elementary process of E ₃ ( f ₀ + 2δf) also occurs. When the intensity of these wavelength-converted lights is high, E ₂ (f ₀ −δf) acts as pump light for the probe light E ₀ , and E ₄ (f ₀ −2δf) = χ ⁽³⁾ E ₂ E ₀ ^* E ₂ again E
₃ (f ₀ + 2δf) acts as pump light for the probe light E _{1 and} generates E ₅ (f ₀ + 3δf) χ ⁽³⁾ E ₃ E ₁ ^* E ₃ . In the same process, new wavelength-converted light with the same frequency interval δf as E ₆ , E ₈ , ... on the low frequency side of E ₄ , and E ₇ , E ₉ , ... on the high frequency side of E _5. It has a great feature that the spectrum is gradually spread and a plurality of wavelength-converted lights of two or more waves can be obtained with respect to the two-wavelength input light.

FIG. 5 is a diagram illustrating a configuration of a multi-wavelength light source that is a first application example of the present invention. A wavelength converter 51 having multi-wavelength output light as shown in the second embodiment, an optical demultiplexer 52 for separating each wavelength, a saturated optical amplifier 53-1 prepared for each wavelength,
53-2, ... 53-n and optical modulators 54-1, 54-2, ... 54-n,
Finally, a multi-wavelength light source can be constructed by combining an optical multiplexer 55 for multiplexing these again.
Here, 56-1, 56-2, ... 56-n are drive devices for the respective optical modulators. Features of the multi-wavelength light source, the output light wavelength is arranged at equal intervals, the two input light E _0in the wavelength spacing is the wavelength converter is to be determined only by a frequency difference δf of E _1in, light It can be used as a light source for frequency division multiplexing (FDM) transmission.

FIG. 6 (a) is a diagram for explaining the configuration of the second and third application examples of the present invention, and 61 is the same configuration (11, 1) as in FIG. 1 (a).
2, 13, 14, 15), 62 is an optical delay circuit, 63 is an optical multiplexer, and 64 is an optical demultiplexer. To operate this, add delay time τ to either one of the two wavelength input lights (65 and 66) (66 in this figure), and then add both to the optical multiplexer.
At 63, they are aligned on the same optical axis and input to the wavelength conversion device 61. The output light is guided to an optical demultiplexer 64 (wavelength filter) which is set to pass only the wavelength-converted light and not the two input wavelengths, and the wavelength-converted light output 67 is obtained.

FIG. 6 (b) is a diagram for explaining the operation of the time width variable optical pulse generator which is the second application example with the passage of time, and the input lights 65 and 66 have time widths t _p0 and t _{p1 respectively} . It shall be given in the form of a light pulse that it has. One of 65 and 66 is pump light and the other is probe light. (b) As shown in the figure, 2
An optical pulse having a time width t _p2 of the overlap of two input optical pulses is obtained as the output light 67. This is because, as elementary processes of this wavelength conversion is represented by _{the ^{E 2 = χ (3) E}} 3 E 1 * E, the input light E ₀
This is because E ₂ occurs only when and E ₁ ^* exist at the same time. Therefore, even if the input light pulse widths t _p0 and t _p1 are relatively long, it is possible to obtain output light having an arbitrary pulse width by changing the delay time τ by the optical delay circuit 62.

FIG. 6 (c) is a diagram for explaining the operation of the optical modulator by the optical input according to the third application example with the passage of time, and the input light 65 is repetitive from the mode-locked laser input as the modulated light. 65 pulse trains with a narrow constant time width and 66 input light
The modulated light has a time width wider than the pulse repetition time of. Since the output is obtained as the time overlap of the two input lights, the output light 67 has an optical waveform in which a pulse train of 65 is modulated by the input light 66. In other words, pulse punching can be performed.
At this time, the narrower the pulse width of the input light 65 is, the wider the spectrum width thereof is. Therefore, it is necessary to take a large detuning δf between the two so that the spectra of the input lights 65 and 66 do not overlap on the optical frequency axis. Further, when the light intensity of the pulse train of the input light 65 is made larger than that of the input light 66 and it is made to act as the pump light, the pump light electric field E is calculated from the formula of E ₂ = χ ⁽³⁾ E ₀ E ₁ ^* E _{0. Since} E ₂ is proportional to the square of ₀ , the pulse width of the output becomes narrower than the input pulse of 65. That is, this wavelength converter
Functions as an optical pulse compressor.

In FIGS. 6 (a), (b), and (c), one of the two input lights has a weaker light intensity than the other, as shown in FIGS. 1 (b) and (c). The case where one wavelength-converted light output is obtained has been described, but as in the second embodiment shown in FIG.
It is also possible to operate by setting the two input light intensities to be substantially equal. In this case, it is necessary to set the demultiplexer 64 so that a plurality of wavelength-converted light wavelengths can be individually taken out.
With respect to the wavelength input light, it is possible to easily obtain a plurality of optical outputs whose time widths are variable and whose pulse widths are uniform, or a plurality of short pulse trains punched out in the same pattern.

FIG. 7 (a) is a diagram for explaining the configuration of the optical logic element which is the fourth application example of the present invention, and 71 is the same configuration (11, 12, 13, 14 as in FIG. 1 (a). , 72) is a wavelength converter, 72 is an optical multiplexer, and 73 is an optical demultiplexer. On the input side, dual wavelength input light (74 and 75) for wavelength conversion and 1000 GHz from now on
The third input light 76 having a higher frequency is aligned on the same optical axis by the optical multiplexer 72 and input to the wavelength conversion device 71. The output light is guided to the optical demultiplexer 73, and the wavelength-converted light output 77 generated from the input light of 74 and 75, the output light 78 composed of the sum of the two wavelengths of the inputs 74 and 75, and the output having only the wavelength of the input 76 Three of the lights 79 are taken out individually.

FIG. 7 (b) is a diagram for explaining the relationship between the spectrum of the input to the optical logic element and the amplification gain spectrum of the traveling waveform laser amplifier and the function of each input light. Input light 7
4, 75 are arranged so that wavelength conversion operation occurs at intervals of about several GHz, and when these are input to the wavelength conversion device 71, their amplification gain spectrum changes from 80 when they are unsaturated to 81 when they are saturated. It is assumed that the power level is set as follows. On the other hand, the input light 76 is set to a power level that does not cause gain saturation by itself, and then placed in the optical frequency range where the decrease from the unsaturated gain is large when saturated (the input light 76 is on the high frequency side compared to 74 and 75). To do. Since the input light 76 is separated from 74 and 75 by at least 1000 GHz or more, the carrier fluctuation cannot follow this frequency difference, so that between 74 and 76 or between 75 and 76.
No wavelength conversion operation occurs between the two. Here, the input light 76
Is used to detect the state of amplification gain saturation caused by the other input lights 74, 75. Therefore, the input signals A and B to the present optical logic element are the two input lights 74 and 75, and the input light 76 is a "negative" input to A and B as described later.
It becomes the control light for taking. In order to realize the optical logic operation with the device of this embodiment, the input light 74, 75,
You can enter any two or three of the 76 at the same time.

FIG. 7 (c) is a diagram for explaining the optical logic operation in this device according to the passage of time, and the input lights 74, 75, and 76 are given as pulse trains representing "1" and "0" as shown in the figure. It is supposed to be. In the figure, although the light levels that correspond to the logical values of "1" and "0" are different for each input / output light, they are shown in a standardized form. First, the input signal A,
A case of inputting 74 and 75 as B will be described. As shown in the figure, wavelength conversion occurs only when both input lights are "1", "1" is output to the output light 77, and "0" is output when either one of the inputs is "0". Is output. Therefore, the output 77 gives an AND (logic: AB) output for the inputs A and B. In addition, since a sum of both input lights is obtained by using a filter that allows both input lights to pass through at the optical output 78, there is no light only when both input lights are "0", and the output becomes "0". . Therefore, output 78 is input A, B
OR (logical sum: A + B) output for In addition,
In this case, even if the control light 76 exists at the same time as the two input signal lights 74 and 75, since the light 76 is so small that the gain saturation does not occur, it does not affect the theoretical output results of the outputs 77 and 78. Absent.

Next, a case where the input signal A (74) and the control light 76 are input will be described. In the output light 79 corresponding to the control light 76,
When light is present in the signal A (“1”), the light output is reduced due to gain saturation (“0”). Conversely, when there is no light in the signal A (“0”), the control light 79 Is amplified with a large unsaturated gain and the optical output of 79 increases (“1”). Therefore,
Output 79 provides the NOT output for input A. Similarly, when two of the input signal B (75) and the control light 76 are input, the negation of B is obtained at the output 79. Output 76
Is "0", the output 79 also remains "0".

When three input signals A (74) and B (75) and the control light 76 are input at the same time, the levels of the output light 79 are “0” for both two input lights and one is “1”. , Both have a light level of 3 and have three light levels. If the upper two light levels are set as the logic level of "1" and "0" of this output, this is the NOR for inputs A and B. Give output. Also, if the lower two light levels are set as the logical levels of "1" and "0" of this output, the NANAD for the inputs A and B is set. Output is obtained. In order to obtain the above-mentioned OR output, NOR output, and NAND output shown here, it is necessary to make the logic levels of "0" and "1" correspond to appropriate light levels as shown in the figure. However, this can be easily realized by connecting an optical bistable element having a threshold value set for each light level to each light output terminal.

In FIGS. 7 (a), (b) and (c), one of the two input lights has a weaker light intensity than the other, as shown in FIGS. 1 (b) and (c). The case where one wavelength-converted light output is obtained has been described, but it is also possible to operate by setting two input light intensities substantially equal to each other as in the embodiment of FIG. 2 shown in FIG. In this case, it is necessary to set the demultiplexer 73 so that a plurality of wavelength-converted light wavelengths can be individually taken out, but the AND outputs for the two inputs A and B can be taken out at a plurality of light wavelengths, and the OR output. Compared with, there is an advantage that the fan-out of the AND output terminal having a small optical output can be increased.

In all of the above-described embodiments, a wavelength conversion device based on a normal semiconductor laser 11 in which light is guided in a plane parallel to the active layer and constitutes a resonator as shown in FIG. 1 (a) is used. As described above, the high-performance wavelength conversion function based on non-degenerate four-wave mixing, which is the main object of the present invention, is possible only by using a high gain, broadband semiconductor amplification medium as a highly efficient optical nonlinear medium. It will be. Therefore,
It is not possible to realize a high-performance wavelength conversion device by applying a highly accurate antireflection film not only to a normal semiconductor laser but also to a so-called surface emitting laser in which an optical resonator short in the direction perpendicular to the active layer surface is formed. Have no argument.

(Advantages of the Invention) As described above, the present invention in which two light waves having different frequencies are incident in the same traveling direction on a traveling waveform laser amplifier which eliminates reflection on both end faces of a semiconductor laser and is a semiconductor gain medium having a high gain and a wide band. The wavelength conversion method and device of the present invention can realize a high-performance wavelength conversion operation having features such as high efficiency, wide band, high stability, and unidirectional output. It has an advantage that it can be easily applied to optical pulse punching and optical logic devices.

[Brief description of drawings]

FIG. 1 (a) is a block diagram of a device of the present invention which is a first embodiment,
FIGS. 1 (b) and 1 (c) show the spectrum of the input light used in the device of the present invention and the obtained output light spectrum, and FIG. 2A to 2G show the experimental result of the output optical spectrum showing the wavelength conversion operation of the first embodiment, and FIG. 3 shows the experiment of FIG. It is a plot of the resulting signal light, pump light, and probe light output with respect to the detuning frequency, and shows the wide band property of the wavelength conversion operation. 4 (a) and 4 (b) are input light and output light spectra of the wavelength conversion device for obtaining wavelength-converted output light of two or more waves according to the second embodiment, and FIG. 5 is a first application example. FIG. 6 (a) is a block diagram of a multi-wavelength light source, FIG. 6 (a) is a block diagram of second and third application examples, and FIG. 6 (b) is a second application example of a time width variable optical pulse generator. FIG. 6C is a diagram for explaining the operation, and FIG. 6C is a diagram for explaining the operation of the optical modulator which is the third application example. FIG. 7 (a) is a block diagram of an optical logic device which is a fourth application example of the present invention, and FIG. 7 (b) is a diagram for explaining the arrangement of each input light necessary for realizing the operation. Figure, Figure 7
(c) is a diagram for explaining various logical operations that can be realized by this device. 11 …… Semiconductor laser 12 …… Active layer waveguide 13,14 …… Current injection terminal 15 …… Anti-reflection film 16 …… Multiplexer 17 …… Input light 18 …… Output light 51 …… Two or more wavelengths Wavelength converter with converted output light 52 …… Optical demultiplexer 53-1,53-2,… 53-n …… Saturation optical amplifier 54-1,54-2,… 54-n …… Optical modulator 55 ...... Optical multiplexer 56-1,56-2,… 56-n …… Optical modulator driver 61 …… Wavelength converter 62 …… Optical delay circuit 63 …… Optical multiplexer 64 …… Optical demultiplexer 65 , 66 …… 2-wavelength input light 67 …… Wavelength conversion output light 71 …… Wavelength converter 72 …… Optical multiplexer 73 …… Optical demultiplexer 74,75 …… 2-wavelength input light (wavelength conversion operation) Input signal: A, B) 76 ... weak third input light (control light) placed on the high frequency side 77 ... Wavelength conversion output light (AND output) 78 .... Two wavelengths of input (74, 75) Output light composed of sum (OR
Output) 79 …… Control light input 76 output light (negative output) 80 …… Unsaturated gain spectrum when there is no input light 81 …… Saturation gain spectrum when there is input light (74, 75)

Claims (2)

[Claims] 1. An optical amplifier having an antireflective film formed on an optical resonator surface of a semiconductor laser, by inputting two light waves having different frequencies, whose polarization planes are not orthogonal to each other, in the same direction,
A semiconductor laser wavelength conversion method, characterized in that output light whose wavelength is converted in the traveling direction of input light is extracted. 2. A semiconductor laser wavelength converter comprising a semiconductor optical amplifier having an optical resonator surface of a semiconductor laser provided with a current injection terminal and an anti-reflection film, and an optical multiplexer on its input side. .