JP2681274B2 - Semiconductor light emitting device and method of operating the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A semiconductor having a structure suitable for high-speed light intensity modulation.
Regarding body light emitting device and its operating method, speed up by removing the conventional upper limit of modulation frequency
In addition, even if a large optical output is taken out, the high speed is affected.
Furthermore, there is a vibration in the light output so that
(1) Optical reflectors that make a pair and face each other to cause laser oscillation.
And guide the light reflected by the light reflector to generate laser oscillation.
An amplification section having an amplification function to cause the paired light
Of the light emitting layer formed between the reflectors and between the light reflectors.
Gain or absorption of light is passed between the light reflectors.
Change it at a cycle less than or equal to the time required to recover
To obtain the first gain modulation section and the amplification section, and
Is formed to extend outside the pair of light reflectors, and
The gain or absorption in that part of the light
At a cycle that is less than or equal to the time cycle required to make one round trip
A second gain modulator that can be changed,
The gain modulator, the amplifier, and the second gain modulator are semiconductor substrates.
Light guide layer and light emitting layer and clad formed on top
An optical waveguide composed of layers and continuous over the entire length,
And the second gain modulation of the pair of light reflectors.
The light reflector on the side close to the part includes the semiconductor substrate and the light guide layer.
It is characterized by the periodic unevenness formed at the interface of
Or, (2) Optical reflectors that face each other and generate laser oscillation.
And guide the light reflected by the light reflector to generate laser oscillation.
An amplification section having an amplification function to cause the paired light
Of the light emitting layer formed between the reflectors and between the light reflectors.
Gain or absorption of light is passed between the light reflectors.
Change it at a cycle less than or equal to the time required to recover
To obtain the first gain modulation section and the amplification section, and
Is formed to extend outside the pair of light reflectors, and
The gain or absorption in that part of the light
At a cycle that is less than or equal to the time cycle required to make one round trip
A second gain modulator that can be changed,
The gain modulator, the amplifier, and the second gain modulator are semiconductor substrates.
Light guide layer and light emitting layer and clad formed on top
An optical waveguide composed of layers and continuous over the entire length,
And the second gain modulation of the pair of light reflectors.
The light reflector on the side close to the part includes the semiconductor substrate and the light guide layer.
It is characterized by the periodic unevenness formed at the interface of
In a method of operating a semiconductor light emitting device, the light is the light reflector.
The first cycle is the same as the time cycle required to make one round trip between
The gain or absorption in the gain modulator of the
Mode-locked oscillation depending on the gain and absorption
The second gain modulation with a signal synchronized with the period
By changing the gain or absorption in the department
The purpose is to control the light corresponding to the signal pattern you want to receive.
Signal pattern equivalent to that of light intensity modulation
It is characterized by outputting. [Field of Industrial Application] The present invention provides a structure suitable for high-speed light intensity modulation.
The present invention relates to a semiconductor light emitting device and a method of operating the same. [Prior Art] As a light intensity modulation method conventionally used for optical communication
Is a semiconductor laser or a light emitting diode
ing diode (LED) itself, which directly modulates the light intensity, or
The light output from the light emitting device is externally modulated.
It is known that external modulation is used to modulate light intensity using a device.
I have. FIG. 7 is a diagram for explaining the case of performing direct modulation.
Fig. 8 shows the circuit diagram of the part and Fig. 8 shows the case of performing external modulation.
The respective main circuit diagrams for the explanation are shown. In each figure, 61 is a semiconductor laser having a pn junction, 62
Is a signal generator for modulation, 63 is a power supply for DC bias, and 64 is an external
The partial modulators are shown respectively. Modulated by a circuit as seen in FIGS. 7 and 8.
In either case, the pulse is applied.
Light is emitted or extinguished according to the time
The shape of the light pulse, i.e. the time width, is the
It is said to be almost the same. [Problems to be Solved by the Invention] In the circuit shown in FIG. 7 and FIG.
That the shape of the output pulse and that of the output pulse match
The point is actually a floating inductive capacitance or element
Delay or waveform distortion due to the effect of parasitic capacitance
However, there is a drawback that the upper limit of the modulation frequency is limited.
is there. 9 and 10 illustrate the above drawback in more detail.
(A) is an input in all figures.
Waveform of current or voltage, and (B) Wave of optical output
Representing each shape, the horizontal axis is time and the vertical axis is current
Alternatively, it takes voltage or light output. According to Fig. 9, it takes time to rise or fall.
Pulse whose time is completely zero, that is, ideal
The response of the laser assuming a pulse is applied is explained.
Will be revealed. In the figure, 65 is the waveform of the input current or voltage,
66 is the optical output waveform that is the response of the laser, and t1 and t2 are the optical output.
Rise and fall delays seen in force waveform 66
These are shown respectively. Thus, when the delays t1 and t2 are present, the light output is
The pulse width of force cannot be narrower than t1 + t2,
Therefore, the upper limit of the modulation frequency is the frequency with a period twice as long as t1 + t2.
It has the drawback of being limited to wavenumber, which is a direct modulation.
Then, it is common regardless of external modulation. Also, as seen in Fig. 9, the response delay is linear.
, The upper limit of the frequency is the signal swing required for driving.
In particular, it directly modulates the semiconductor laser, depending on the width
In some cases, it requires a relatively large current,
T1 and t2 increase, and the upper limit of the modulation frequency decreases.
There is a drawback to that effect. Furthermore, the light intensity is increased to increase the transmission distance.
If it is necessary to modulate with large amplitude and high power,
As seen in Fig. 9, when the response delay is linear.
In this case, the larger the amplitude, the larger the delays t1 and t2.
In the case of direct modulation, the speed increases as the light output increases.
There is a drawback that the property is lowered. According to Fig. 10, another drawback of direct modulation is explained.
Will be revealed. In the figure, 67 is the waveform of the input current or voltage,
68 shows the waveform of the optical output which is the response of the laser.
I have. The input current or voltage waveform 67 has no delay.
It is shown in consideration. If the laser diode is directly modulated, it will be
Vibration of the optical output occurs due to the vibration of the excitation density of the rear.
This vibration may last for nanoseconds, which causes the waveform to
Distortion, the disadvantage that the light output of a good pattern is not obtained
is there. Based on the above, the present invention provides a modulation frequency.
Speed up by removing the conventional upper limit in number,
Do not affect the high speed even if you take out the appropriate optical output
In addition, it is possible to suppress the vibration of the light output.
To do. [Means for Solving Problems] FIG. 1 shows a semiconductor light emitting device for explaining the principle of the present invention.
FIG. In the figure, 1 is a semiconductor substrate, 2 is an optical waveguide layer, and 3 is
The semiconductor layers forming the amplification section, 4 are gain modulations for mode locking.
The semiconductor layers 5 and 5 block the light output from the amplifier.
Alternatively, a semiconductor that forms a gain modulator that is modulated by transmitting light.
Layers 6, 6 and 7 are reflectors or phases for returning light
The first mirror surface and the second mirror surface, and 8 is amplification
Section, 9 is a gain modulator for mode locking, and 10 is a gain modulator for light intensity modulation.
An optical modulator and an optical modulator 11 are shown respectively. FIG. 2 is a main part of the semiconductor light emitting device shown in FIG.
FIG. 3 is a diagram showing a signal waveform in FIG. In the figure, 12 is a gain modulation applied to the gain modulator 9.
Signal, 13 is an optical signal immediately below the gain modulator 9, and 14 is an optical signal.
An optical signal directly below the modulator 10 and a gain-modulated signal 12
Synchronization signal (clock pulse) formed based on
16 is a target signal pattern for modulating light, and 17 is a signal pattern.
It is generated by the signal of "1" in the pattern 16 and the synchronizing signal 15.
Generated trigger signal, 18 is "0" in signal pattern 16
Trigger signal generated by the signal and sync signal 15
Is set by trigger signal 17 and reset by trigger signal 18.
The gate signal applied to the gain modulation unit 10 is
The shutter function of the modulator 10 is obtained, that is, the gate signal 19 is "1".
Modulates by transmitting light at the time of and blocking light at the time of "0"
L is the distance between the first mirror surface 6 and the second mirror surface 7.
Distance T is the period of the gain modulation signal 12, respectively. Here, the signal indicated by the broken line in the signal pattern 16 is
“0” is also indicated by the broken line in the optical signal 20 which is the output signal.
The signal shown is blocked by the gain modulator 10 and output to the outside.
Light that does not exist in the optical waveguide layer 2
Refractive index of light in n, speed of light in vacuum is c, period
In T, the light makes one round trip between the first mirror surface 6 and the second mirror surface 7.
The same time (T = 2nL / c) as the time required for By the way, the gain modulator 9 has a cycle T of 2nL / c.
Applying modulation signal 12 to gain modulation,
All the phases of light with different frequencies match
And a pulsed oscillation with a very short time width
I will get up. This is called the mode-locked oscillation state
And activate mode synchronization in the manner described above.
Live mode synchronization. In mode synchronization
The pulse width is, when the full width at half maximum of the optical spectrum is df,
It will be about 1 / df. For example, with 1.3 [μm] light,
When the width of the rule is 1 [nm], df = (3 * 10 ^ 8 / 1.3 * 10 <-6>) * (1 * 10 ^ <-9> /1.3*10 ^ <-6> = 1.77 * 10 ^ 11 Here, <-6> etc. shall indicate the power of square (the same applies below.
Therefore, the pulse width w during mode synchronization is about w = 1 / df = 1 / (1.77 * 10 ^ 11) = 5.6 * 10 ^ <-12> = 5.6 [psec]. Next, since the period T is given by 2nL / c, L = 2 [m
m], n = 3.6, c = 3 * 10 ^ 8, T = 48 [pse
c], which is about 20 GHz in frequency conversion.
The period T changes depending on the distance L. As you can see from the above, mode synchronization
Therefore, a very fast light pulse can be obtained,
Moreover, when it is carried out, the energy during the period T during continuous oscillation is
The total energy equivalent to gi is collected in a light pulse of width w
Therefore, the pulse peak power is T / w times,
High output light pulse and conventional direct modulation
Alternatively, it extracts energy with higher efficiency than external modulation.
be able to. The pulse train of the light generated in this way is represented by symbol 13 and
The optical signal indicated by 14, the optical signal 13 is a sine wave.
Is generated at the moment when the amplitude of the gain modulation signal 12
In addition, the optical signal 14 is
Time required to travel through the gain modulators 9 to 10 in 2
Just delayed. The modulation by the gain modulation signal 12 as described above is performed by, for example, an electric signal.
Current or change the reverse bias current to the pn junction.
Electrically, such as applying a pressure signal to change the absorption rate
Therefore, the synchronization signal 15
The signal pattern that you want to generate and
The trigger signal 17
And pick up 18 Furthermore, depending on the logic circuit,
Set by trigger signal 17 and reset by trigger signal 18.
To generate a gate signal 19, which is then
ANDed with the optical signal 14 which is an optical pulse train applied to the modulator 10.
Is the modulated optical pulse train of interest.
The optical signal 20 is obtained. In the operation described above, the gain modulator 10 is a kind of shutter.
Since it acts like a filter, the waveform of the cut optical pulse is
Has a shape similar to the optical signals 13 and 14, and
Oscillation at the rising edge of an optical pulse as seen by contact modulation
Does not occur at all. Also, according to the prior art, the optical signal 20
To obtain an optical pulse train such as
Of the rising and falling delay time of the gain modulation signal
Sum, that is, t1 + t2 shown in Fig. 9 is not less than T / 2
The means described with reference to FIGS. 1 and 2
If the rise time and the fall time of the optical signal 20
The sum of the intervals is equal to or less than the period T.
A double speedup is achieved with a dynamic device. Further
Further, as described above, the gain modulation signal 12 is a sine wave.
And, as compared with the case of performing light intensity modulation, low energy
Modulation based on Rugi is sufficient, so high frequency is easy
In addition to this, synchronization signal 15, signal pattern
16 and trigger signals 17 and 18 are all used in logic circuits.
Therefore, it is lower than the power used for light intensity modulation.
It is easy to speed up from this aspect as well.
The most difficult thing to speed up here is the gain variation.
The gate signal 19 applied to the adjustment unit 10 is as described above.
As described above, according to the present invention, the speed can be doubled as compared with the conventional one.
You. From the above, the semiconductor light emitting device according to the present invention is
(1) Optical reflectors that face each other and generate laser oscillation.
(For example, the first mirror surface 6 and the second mirror surface 7: see FIG. 1),
The light reflected by the light reflector is guided to cause laser oscillation.
An amplifying section having an amplifying function (for example, amplifying section 8: FIG. 1)
And a light reflector formed between said pair of light reflectors and
The gain or absorption of light in the light emitting layer between the light reflectors
Same as the time period required for the light to make one round trip between the light reflectors.
A first gain modulator that can be changed with a period of less than about
For example, the mode-locking gain modulator 9: see FIG. 1) and the amplification
And extend outside the pair of light reflectors.
Formed in the same way, and gain or absorption in that part
Is the same as the time period required for light to make one round trip between the light reflectors.
A second gain modulator that can be changed with a cycle of less than about
For example, the light intensity modulation gain modulator 10: see FIG. 1),
The first gain modulator, the amplifier, and the second gain modulator
Is a stacked type on a semiconductor substrate (eg substrate 21: see Fig. 5)
The formed light guide layer (for example, light guide layer 22: see FIG. 5)
Light) and the light emitting layer (for example, light emitting layer 23: see FIG. 5) and black.
Consists of a rud layer (eg clad layer 24: see FIG. 5)
Optical waveguide that is continuous over the entire length (for example, optical waveguide layer
2: See FIG. 1) and of the pair of light reflectors
Of these, the light reflector on the side close to the second gain modulator is the half
Periodic irregularities formed at the interface between the conductor substrate and the light guide layer
(For example, the unevenness 32 forming one light reflector: see FIG. 5)
Or (2) a pair of optical reflectors facing each other to cause laser oscillation.
And guide the light reflected by the light reflector to generate laser oscillation.
An amplification section having an amplification function to cause the paired light
Of the light emitting layer formed between the reflectors and between the light reflectors.
Gain or absorption of light is passed between the light reflectors.
Change it at a cycle less than or equal to the time required to recover
To obtain the first gain modulation section and the amplification section, and
Is formed to extend outside the pair of light reflectors, and
The gain or absorption in that part of the light
At a cycle that is less than or equal to the time cycle required to make one round trip
A second gain modulator that can be changed,
The gain modulator, the amplifier, and the second gain modulator are semiconductor substrates.
Light guide layer and light emitting layer and clad formed on top
An optical waveguide composed of layers and continuous over the entire length,
And the second gain modulation of the pair of light reflectors.
The light reflector on the side close to the part includes the semiconductor substrate and the light guide layer.
It is characterized by the periodic unevenness formed at the interface of
In a method of operating a semiconductor light emitting device, the light is the light reflector.
The first cycle is the same as the time cycle required to make one round trip between
The gain or absorption in the gain modulator of the
Mode-locked oscillation depending on the gain and absorption
The second gain modulation with a signal synchronized with the period
By changing the gain or absorption in the department
The purpose is to control the light corresponding to the signal pattern you want to receive.
Signal pattern equivalent to that of light intensity modulation
It is characterized by outputting. [Operation] By adopting the above means, the semiconductor light emitting device is
Synchronous oscillation, extremely short emission time width and repeated
A high-frequency optical pulse can be obtained and mode-locked
Transmitted in synchronization with the light emission cycle of the shaken semiconductor light emitting device
The second control mechanism modulates the signal pattern with
The transmission of light is controlled by the shutter action, and the required optical pulse train is not formed.
Since it outputs a signal pattern that
It is possible. [Embodiment] FIGS. 3 (A) and 3 (B) are main part slopes of one embodiment of the present invention.
FIG. 1 and FIG.
The same symbols used in the figures indicate the same parts or
They have the same meaning. In the figure, 21 is an n-type InP substrate and 22 is an n-type InGaAsP optical module.
Id layer, 23 is an InGaAsP light emitting layer (active layer), and 24 is a p-type InP layer.
Rad layer, 25, 26, 27 are p-type InGaAsP contact layers, 28 is
The electrode of the amplification section, 29 is the electrode of the gain modulation section for mode locking, and 30
Is an electrode of the gain modulator for light intensity modulation, 31 is a common electrode, 33
The reference numerals 34 and 34 are films (not shown) for forming a high light reflection film.
35) is an anti-reflection film (not shown), 46 lines
Reference numeral 47 designates the amplifier 8 and the gain modulator 9, and the amplifier 8 and
Separation grooves for electrically separating the gain modulator 10 respectively,
51 is a p-type InP current block layer, 52 is an n-type InP current block
Layer 53 is made of a silicon dioxide film or a silicon nitride film.
The dielectric films 54, 55, 56 and 57 are provided in the gain modulators 9 and 10.
Isolation groove to reduce the capacitance of the waveguide area
The part including the waveguide, 59 and 60 are the parts not including the optical waveguide
Are shown respectively. In the present embodiment, the substrate 21, the light guide layer 22, the light emitting layer 2
3, the clad layer 24 constitutes an optical waveguide, and this optical waveguide
The gain modulator 9, the amplifier 8, and the gain modulator 10 are continuous.
You. In addition, the grooves 46 and 47 are the portion 59 and the portion not including the optical waveguide.
In 60 and 60, it reaches the substrate 21, but the optical waveguide
In the containing portion 58, the current blocking layer 52 remains.
You. Furthermore, the electrodes 29 and 30 are used for lead bonding.
It should be the minimum required area, as shown in Figure (A).
As you can see, the part on the left side is cut off
You. FIGS. 4A and 4B show another embodiment of the present invention.
It shows a perspective view and a side view of the essential part of the
The same symbols as those used in FIGS. 3 to 3 indicate the same parts.
Or have the same meaning. This embodiment is different from the embodiment described with reference to FIG.
The points do not include the optical waveguides in the gain modulators 9 and 10.
The only difference is that parts 59 and 60 have been removed.
Yes, everything else remains the same. FIG. 5 shows the semiconductor described with reference to FIGS. 3 and 4.
FIG. 1 is an explanatory view of a main part including a light emitting device and necessary devices.
The symbols used in Figures 4 to 4 represent the same parts.
Or have the same meaning. In addition, the semi-conductor shown
The body light emitting device operates according to the embodiment shown in FIGS. 3 and 4.
Is for explaining. In the figure, reference numeral 32 denotes an unevenness (corrugation) which constitutes one of the light reflectors.
33) and 33 and 34 are light reflectors of the other, high light reflection
Dielectric film and metal film forming the film, 35 is a light antireflection film, 36 is
A DC power supply for applying a DC current to the amplification section 8 for amplification.
Source, 37 is a signal generator, and 38 is a clock signal that is a synchronization signal.
Device for forming a rule, 39 is a delay device, and 40 is a signal to be transmitted.
No. signal pattern, 41 is a serial-parallel converter, 42 is
Set signal, 43 is reset signal, 44 is set / reset
・ Flip-flop circuit, 45 is gain modulation for light intensity modulation
Apply a current or voltage that provides sufficient power to drive part 10.
Generated drive circuit, 48 is a DC bias power supply
Is shown. In this structure, the dielectric film 33 is made of silicon dioxide.
Film or silicon nitride film, and the metal film 34
Then, a metal film or the like can be used. In this embodiment, the DC power supply 36 and the DC bias are used.
Power is supplied from the power supply 48 for normal semiconductors.
Laser oscillation similar to laser is performed. In this case, the metal film 34
And the unevenness 32 become a pair of light reflectors to form a resonator.
The cavity length L of the metal film 34 and the dielectric film 33
It becomes the length between the center. Optically, this length and light
The product of the refractive index n of the waveguide, that is, nL is the resonator length. Ma
The gain modulator 9 applies a forward bias voltage to
High frequency is superposed on this to change the positive gain in high frequency.
Operates as a gain modulator, or reverse bias
Voltage is applied, and a high frequency is superimposed on it, and Franz Ke
Use the Franz-Keldish effect and
Operates as a gain modulator that changes gain (absorption) at high frequencies
You can let me make it. Furthermore, regarding the gain modulator 10,
High extinction ratio to light and high speed response
Since it is required to have responsiveness, the backward via
Voltage is applied and the Franz-Keldysh effect is used
It is better to operate as a gain modulator that depends on the absorption.
In the above description, the resonator length L is defined by the metal film 34 and the dielectric.
As the length between the surface of the body membrane 33 and the center of the unevenness 32,
Here, the "center of the unevenness 32" is taken as the unevenness 32
Acts as a mirror over all areas,
Because it has the meaning to represent the average length
You. FIG. 6 is a main part of the semiconductor light emitting device shown in FIG.
2 is a diagram showing a signal waveform in FIG.
The same symbols as those used to indicate the same parts or have the same meaning.
Let's do it. In the figure, 12 is the output of the signal generator 37,
Gain modulation, which is an electrical signal applied to the electrode 29 of the modulator 9
The signal is shown. 13 is an optical signal in the gain modulator 9.
Therefore, it shows the change over time of the light intensity in the light emitting layer 23.
Reference numeral 14 denotes an optical signal in the gain modulator 10 in the light emitting layer 23.
Shows the light intensity of. 15 is the output of the signal generator 37
Clock pulse generator 38 based on gain modulated signal 12
2 shows the sync signal formed in FIG. 15B is synchronous
A signal obtained by delaying the signal 15 by the delay device 39 is shown.
You. 16 is one of the target signal patterns for modulating light
An example is shown. 17 is the theory of the serial-parallel converter 41
Signal and delay of "1" in signal pattern 16
Generated by the synchronized sync signal 15B.
Shows the trigger signal that becomes the set signal for the flip-flop circuit 44.
doing. 18 is also the theory in the serial-parallel converter 41
Signal and delay of "0" in signal pattern 16
Also generated and set with the sync signal 15B
・ Trip that becomes the reset signal of the flip-flop circuit 44
A moth signal is shown. 19 is the rising edge of trigger signal 17
It is set at the edge and the trigger signal 18 rises.
Set-reset flips reset on the edge of
· Obtained from flop circuit 44 and applied to gain modulator 10
The gate signal is shown. 20 applies the gate signal 19
The gain modulator 10 driven via the drive circuit 45.
The optical signal 14 when the gate signal 19 is "1"
Modulated by blocking the optical signal 14 when it is “0”.
Shows the optical signal which is the output corresponding to the signal pattern 16.
ing. The modulation action, that is, absorption, in the gain modulator 10 described above.
The effect is small when the gate signal 19 is at a high level.
On the contrary, increase it when it is at a low level
It is. Therefore, the output designated by the symbol 49 in FIG.
That is, the optical signal 20 seen in FIG.
Equal to the AND of the output signals 19 and is obtained accordingly
Things. In the figure, the waveform shown by the broken line is
Either “0” or absorbed and output to the outside.
It means that it is not possible. Illustrating the dimensions of the main parts shown in FIG. 5,
The metal film 34 that is one mirror surface and the center of the unevenness 32 that is the second mirror surface
The distance L between them is 2 [mm], and the length of the gain modulator 9 is 50 [μ
m], the length of the gain modulator 10 is 200 [μm], and the separation grooves 46, 4
The width of 7,54,55,56,57 is 10 [μm], between the separation grooves 54 and 55,
The width between the separation grooves 56 and 57 is 5 [μm], and
Pitch of convex 32 is 400 [nm], depth is 100 [nm], light guide
Energy band of InGaAsP forming the layers 22 and 23
The size of the gap is 1.15 (μ
m] and 1.3 [μm], and their thickness is 0.1 [μm]
m] and 0.2 [μm], and their widths are both 1 [μm]
is there. In addition, the time period and frequency of each signal are
Signal 12, optical signal 13, optical signal 14, modulated optical signal 20, etc.
The repetition cycle is 56 [psec], that is, about 18 in frequency conversion.
[GHz], the minimum width of the gate signal 19 is 56 [psec].
As already mentioned, under the above configuration and driving conditions
Then, the light that reciprocates in the light emitting layer 32 between the metal film 34 and the unevenness 32
Is a pulsed state as indicated by symbol 13 in FIG.
It has a light intensity distribution. Also, in FIG.
When the indicated modulation signal is 18 GHz, the light in the light emitting layer 23
Spread of at least greater than 5 [Å]
Therefore, when the pulsed light in the light emitting layer 23 is pulsed at this time,
The space is smaller than 12 [psec]. [Effects of the Invention] In the semiconductor light emitting device and its operating method according to the present invention,
The semiconductor light emitting device is
Optical pulse with extremely short width and high repetition frequency
Emitting semiconductor light that is oscillating and is mode-locked
With the signal pattern that you want to transmit in synchronization with the light emission cycle of the device
The gain modulator performs the modulation operation, and its shutter action
A signal pattern that controls the transmission and consists of the required optical pulse train
Is output. According to the present invention, by adopting the above-mentioned configuration,
Compared to surgery, it is possible to perform optical modulation at twice the high speed.
If, for example, a pulse of 56 [psec] is used,
With conventional technology, the RZ (return to zero) signal is approximately 9 [GH
z) was the limit of modulation, but according to the present invention, about 1
Modulation is possible up to 8 [GHz]. In the prior art,
For example, modulation to a level that gives an optical output equivalent to 10 [mW]
However, the pulse width is 5 [GHz] and the duty ratio is 50 [%].
Energy output by a single "1" signal
G is the pulse width (100 [psec]) and output (10 [mW])
The product is 1 [pJ], but according to the present invention, mode synchronization is performed.
1 cycle (200 [psec])
Since the energy between them is concentrated in one pulse, double the energy
It is possible to transmit nergie (2 [picojoules])
is there. Furthermore, in the prior art, when direct modulation is performed,
In this case, the vibration of the output optical signal was a problem, but the present invention
According to, such vibration does not occur.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional side view of a main part of a semiconductor light emitting device for explaining the principle of the present invention, and FIG. 2 is a signal in a main part of the semiconductor light emitting device shown in FIG. Waveform diagrams, FIGS. 3 (A) and 3 (B) are a perspective view and a sectional side view of a main part of one embodiment of the present invention, and FIGS. 4 (A) and 4 (B) are the present invention. FIG. 5 is a perspective view of a main part of another embodiment and a side view of the main part cut off. FIG. 5 is a semiconductor light-emitting device for explaining the operation of the embodiment shown in FIG. 3 and FIG. Figure, 6th
5 is a diagram showing signal waveforms in the main part of the semiconductor light emitting device shown in FIG. 5, FIGS. 7 and 8 are circuit diagrams of main parts for explaining the prior art, and FIG. 9 (A). And (B) and
FIGS. 10A and 10B are diagrams showing input / output waveforms, respectively. In the figure, 1 is a semiconductor substrate, 2 is an optical waveguide layer, a semiconductor layer that constitutes a gain modulation section, and 5 is a semiconductor that constitutes a gain modulation section that modulates light output from the amplification section by blocking or transmitting it. Layers 6 and 7 are reflectors for returning light or equivalents thereof, and a first mirror surface and a second mirror surface, 8 is an amplifying section, 9 is a mode-locking gain modulating section, and 10 is a light intensity modulating section. A gain modulation section, 11 is an optical output section, 12 is a gain modulation signal applied to the gain modulation section 9, 13 is an optical signal directly below the gain modulation section 9, and 14 is an optical signal directly below the gain modulation section 10. Signal, 15 is a synchronization signal (clock pulse) formed based on the gain modulation signal 12, 16 is a target signal pattern for modulating light, and 17 is a signal of "1" in the signal pattern 16. And the trigger signal generated by the sync signal 15, and 18 is the signal pattern
The trigger signal generated by the signal of "0" in 16 and the synchronization signal 15, 19 is the gate signal applied to the gain modulator 10 which is set by the trigger signal 17 and reset by the trigger signal 18, and 20 is The optical signal modulated by the shutter action of the gain modulator 10, that is, the action of transmitting light when the gate signal 19 is "1" and blocking the light when the gate signal 19 is "0", L is the first mirror surface 6 and the second The distance between the mirror surfaces 7 and T indicate the period of the gain modulation signal 12, respectively.

Claims (1)

(57) [Claims] A pair of light reflectors facing each other to generate laser oscillation, an amplification section having an amplification function of guiding light reflected by the light reflector to cause laser oscillation, and the pair of light reflectors Between the light reflectors formed between the light reflectors and changing the gain or absorption of the light in a period equal to or less than the time period required for the light to make one round trip between the light reflectors. One gain modulator and the amplifier are formed to extend outside the pair of light reflectors that are continuous with the amplification unit, and the light gains or absorbs light in that portion between the light reflectors. A second gain modulator that can be changed at a period equal to or less than the time period required for one round trip, wherein the first gain modulator, the amplifier, and the second gain modulator are laminated on a semiconductor substrate. Comprised of the formed light guide layer, light emitting layer and clad layer The optical reflector that forms a continuous optical waveguide and that is closer to the second gain modulation portion of the pair of optical reflectors is formed at the interface between the semiconductor substrate and the optical guide layer. A semiconductor light-emitting device having periodical irregularities. 2. A pair of light reflectors facing each other to generate laser oscillation, an amplification section having an amplifying function to guide light reflected by the light reflector to cause laser oscillation, and the pair of light reflectors Between the light reflectors formed between the light reflectors and changing the gain or absorption of the light in a period equal to or less than the time period required for the light to make one round trip between the light reflectors. One gain modulation section and the amplification section are formed to extend outside the pair of light reflectors that are continuous with each other, and the gain or absorption at that portion causes light to pass between the light reflectors. A second gain modulator that can be changed at a period equal to or less than the time period required to make one round trip, and the first gain modulator, the amplifier, and the second gain modulator are laminated on a semiconductor substrate. It is composed of the formed light guide layer, light emitting layer and clad layer, Without an optical waveguide consecutive Te,
The light reflector on the side closer to the second gain modulator of the pair of light reflectors is a periodic unevenness formed at the interface between the semiconductor substrate and the light guide layer. In the method of operating a semiconductor light emitting device, a mode is obtained by changing the gain or absorption in the first gain modulator at the same period as the time required for light to make one round trip between the light reflectors. By controlling the gain or absorption in the second gain modulation section with a signal synchronized with the period in which synchronous oscillation is performed and the gain or absorption is changed, the control of light corresponding to the signal pattern to be transmitted is performed. A method for operating a semiconductor light-emitting device, which is characterized in that a signal pattern equivalent to that obtained by light intensity modulation with a target signal is output.