JPH041513B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical amplification method using a semiconductor laser, which amplifies laser input light using a semiconductor laser.

[Conventional technology]

Conventionally, the following principle is explained with reference to FIG.
Optical amplification methods using semiconductor lasers have been proposed. In other words, the opposing end faces are the cleavage planes,
A resonator-type semiconductor laser 1 having a configuration in which the reflective surface is a reflective surface or a reflective film is attached to the opposing end faces is used, and a current below the oscillation threshold is injected from a power source 3 into the active layer 2. In a state where
Laser input light S1 is injected from the outside, the laser input light S1 is amplified by the active layer 2, and the amplified laser output light S of the laser input light S1 is
2 is outputted from the active layer 2 to the outside. The above is the principle optical amplification method using a semiconductor laser that has been proposed so far. In the conventional optical amplification method using a semiconductor laser, the semiconductor laser 1 is operated in a region sufficiently lower than the saturation level, and the laser input light
1 was linearly amplified.

[Problem to be solved by the invention]

For this reason, in the case of conventional optical amplification methods using semiconductor lasers, there is a function to nonlinearly amplify laser input light by shaping the waveform of laser input light into optical pulses, and a function to perform optical logic gates on multiple laser input lights. None of the nonlinear amplification functions could be obtained.

[Object of the present invention]

Therefore, although the present invention employs an optical amplification method using the principle semiconductor laser described above in FIG. 1, we also propose an optical amplification method using a novel semiconductor laser that can obtain the above-mentioned functions. That is.

[Method of the present invention]

In the optical amplification method using the principle semiconductor laser described above in FIG. 1, the power gain G of the semiconductor laser 1 is expressed as the ratio of the power P ₁ of the laser input light S1 to the power P ₂ of the laser output light S2. _T is
Hereinafter, for the sake of simplicity, the semiconductor laser 1 will be described as having a cleavage plane as a reflecting surface, and will be expressed by the following equation. G _T = P ₁ / P ₂ = ηT ² G / {1-RG) ²・(1+F・
sin ² φ)}...(1) F=4GR/(1-GR)2...(2) G=exp{(g-α)l}...(3) g= _g0 /(1+ _P1 / _Ps ) …(4) φ=δ−{(b−2)・g ₀・P ₂ /P _s )}/
(1+ _P2 / _Ps )...(5) Here, the following symbols in formulas (1) to (5) indicate the following. η...Efficiency of light injection into the active layer 2 of the semiconductor laser 1 T...Transmittance of the cleavage plane of the semiconductor laser 1 R...Reflectance of the cleavage plane of the laser input light 1 g...Saturation amplification gain coefficient α... Loss coefficient g ₀ ...Small signal gain coefficient l...Laser length of semiconductor laser 1 _Ps ...Saturation power of laser output light φ...Phase of light per one pass through active layer 2 of semiconductor laser 1 Amount of change δ...Initial detuning b...Ratio of the rate of change of the refractive index of the active layer 2 and the gain coefficient with respect to the density of carriers injected into the active layer 2 of the semiconductor laser 1 (AlGaAs/
For GaAs semiconductor lasers, −0.5 to −
6.2) As a result of various experiments, the present inventors found that in the optical amplification method using the principle semiconductor laser described _above in _FIG . The _relationship is expressed as the second
It was confirmed that the laser input optical power (η·P ₁ /P _s ) versus laser output optical power (P ₂ /P _s ) characteristic had an S-shape as shown in the figure. However, Figure 2 shows the characteristics when small signal gain coefficient g = 28 cm ^-1 loss coefficient α = 10 cm ^-1 laser length l = 500 μm cleavage plane reflectance R = 0.35 initial detuning δ = 2.75 rad . In addition, as a result of various experiments, the present inventors found that the first
In the optical amplification method using the principle semiconductor laser described above in the figure, the relationship between the power P ₁ of the laser input light S1 and the power P ₂ of the laser output light S2 is as follows.
Using the initial detuning δ, which is another parameter of the power gain G _T described above, as a parameter, the laser input optical power (η・P ₁ /P _s ) vs. laser having an S-shape as shown in FIG. Output optical power (P ₂ /
_Ps ) characteristics. However, FIG. 3 shows the characteristics in the case where: small signal gain coefficient g ₀ =28 cm ^-1 loss coefficient α = 10 cm ^-1 laser length l = 500 μm, reflectance R of cleavage plane = 0.35. Based on the above, the present inventors proposed that in the optical amplification method using the principle semiconductor laser described above in FIG. Power (η・P ₁ /
P _s ) vs. laser output optical power (P ₂ /P _s ) characteristics, and the semiconductor according to the present invention nonlinearly amplifies the laser input light described below as laser input light S1 as follows. We have now proposed this method as an optical amplification method using a laser. That is, (a) the power in the active layer 2 is as shown in FIGS. 2 and 3 (a)
Input optical power (η・P ₁ /P s ) vs. output optical power (P ₂ /P _s ) of a laser having an S-shape as shown in FIGS.
P _s ) Laser input optical power (η・P ₁ /
_Ps ) Laser input light having a value exceeding the maximum value is injected as laser input light S1, and the laser input light is nonlinearly amplified in the active layer 2 by shaping the waveform into a light pulse. or (b) A plurality of (for example, two) laser input lights are applied to the active layer 2, and the sum of their powers is as shown in FIGS. 2 and 3.
The input optical power (η・P ₁ /P _s ) versus the laser output optical power (P ₂ /P _s ) Characteristic laser input optical power (η・
P ₁ /P _s ) is injected as laser input light S1 with a relationship exceeding the maximum value, and the plurality of laser input lights are nonlinearly amplified in the active layer 2 in the form of a logic gate. As described above, the optical amplification method using a semiconductor laser according to the present invention has been clarified. From the above, according to the present invention, it is possible to obtain (a) the function of nonlinear amplification by shaping the laser input light into an optical pulse, or (b)
It is clear that the function of nonlinear amplification can be obtained by performing an optical logic gate on a plurality of laser input lights. Furthermore, when using the optical amplification method using the semiconductor laser according to the present invention described above, the laser input optical power (η・P ₁ /P _s ) versus the laser output optical power (P ₂ /P _s ) As is clear from the characteristics, the larger the absolute value of the ratio b between the refractive index of the active layer 2 and the rate of change of the gain coefficient is, the more the value of the initial detuning δ is increased to π. The closer they are, the less power of the laser input light injected into the active layer as the laser input light S1 can nonlinearly amplify the laser input light. Furthermore, when using the optical amplification method using the semiconductor laser according to the present invention described above, the carrier lifetime τ in the active layer 2 of the semiconductor laser 1 is reduced to several nanoseconds (ns).
On the other hand, when the power P ₁ of the laser input light S1 is set to the saturation power P _s described above as 10 mW,
Furthermore, when the light injection efficiency η is 0.5, it is 1 mW, so by simply making the laser input light S1 have an extremely small switching energy of several femjoules (fJ), expressed as P ₁ ×τ,
Nonlinear amplification is possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the principle of an optical amplification method using a semiconductor laser, which is used to explain the optical amplification method using a semiconductor laser according to the present invention. FIGS. 2 and 3 are diagrams showing the S-shaped laser input optical power versus laser output optical power characteristics of a semiconductor laser, for explaining the optical amplification method using the semiconductor laser according to the present invention. 1... Semiconductor laser, S1... Laser input light,
2...Active layer, S2...Laser output light, 3...Power source.

Claims (1)

[Claims] 1. Using a semiconductor laser, injecting a laser input light from the outside while injecting a current below the oscillation threshold into its active layer, the active layer emits the laser input light. In an optical amplification method using a semiconductor laser that amplifies the laser input light and outputs the amplified laser output light from the active layer to the outside, the semiconductor laser has an S-shaped laser input light power versus laser output. applying a laser input light to the active layer, the power of which exceeds the maximum value of the laser input light power on the laser input light power vs. laser output light power characteristic having the S-shape; An optical amplification method using a semiconductor laser, characterized in that the laser input light is injected as the laser input light, and the laser input light is nonlinearly amplified in the active layer in the form of waveform shaping into an optical pulse. 2 Using a semiconductor laser, injecting a current below the oscillation threshold into its active layer, injecting laser input light from the outside, amplifying the laser input light in the active layer, and increasing the laser input In an optical amplification method using a semiconductor laser that outputs amplified laser output light from the active layer to the outside, the semiconductor laser is made to have an S-shaped laser input light power vs. laser output light power characteristic. , A plurality of laser input lights are applied to the active layer, and the sum of their powers has a value exceeding the maximum value of the laser input light power on the above-mentioned S-shaped laser input light power vs. laser output light power characteristic. In relation to
An optical amplification method using a semiconductor laser, characterized in that the plurality of laser input lights are injected as the laser input light, and the plurality of laser input lights are nonlinearly amplified in the form of logic gates in the active layer.