JPS59116625A - Optical pulse generator - Google Patents

Abstract

PURPOSE:To obtain an ultrashort optical pulse by giving optical pulse output of a laser to the first nonlinear Fabry-Perot optical bistable device, giving this transmitted light to the second nonlinear Fabry-Perot optical bistable device, and forming a separator for extracting the reflected light. CONSTITUTION:A GaAs-GaAlAs distribution feedback type semiconductor laser 12 is laminated on a substrate 11. An output pulse from the laser 12 is made incident through a GaAlAs buffer layer 13 to the first optical bistable device 14. The device 14 is prepared by inserting a GaAs-GaAlAs superlattice nonlinear medium 143 between GaAs-A As Bragg reflectors 141, 142. A blazed Bragg connector 15 acts as a 3dB beam splitter. The transmitted light from the connector 15 is made incident to the second optical bistable device 16 constituted like the device 14. The reflected light from the device 16 is separated with the connector 15, and extracted as an ultrashort output optical pulse. Accordingly, an ultrashort pulse can be generated with a small device by small power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical pulse generator that generates extremely short optical pulses of picosecond (PS) class.

[Technical background of the invention and its problems 9 Generation of ultrashort optical pulses is important for various optical applications.

For example, ultrashort optical pulses are required for investigating time-response sounds of optical transitions, high-resolution photometry, ultrahigh-speed optical computers, and optical communications.

Conventionally, in the case of a laser with a sufficiently wide gain width, mode-locking is applied to generate pS-class optical pulses. +
It is known to obtain a light pulse of 4, or to make the leading edge of a light pulse completely steep by using a saturable absorber.

However, in the mode-locking method, if the dispersion of the laser active medium is not sufficiently small, the axial mode spacing will be irregular.
It was difficult to achieve sufficient mode locking, and ultrafast optical gates were required to obtain a single, extremely short optical pulse.

Furthermore, optical pulse narrowing using saturable absorbers generally requires sufficiently high output optical pulses, making it unsuitable for microelectronic applications.

[Purpose of the invention]

It is an object of the present invention to overcome all of the above-mentioned difficulties and to provide a means for inventing ultrashort optical pulses simply and with low power.

[Summary of the invention]

The generation of ultrashort optical pulses according to the present invention utilizes the ultrafast switching characteristics of a nonlinear Fabry-Perot optical bistable device.

The optical input/output characteristics of the nonlinear 7 Abry-Perot optical bistable device are as shown in FIG. A nonlinear 7 Abry-Perot optical bistable device is formed by inserting a nonlinear optical medium into a Fabry-Bello resonator of two mirrors facing each other. It takes advantage of the rapid transition to a resonant state due to a change in the refractive index. That is, the threshold optical power F
Up to T, it is in a non-resonant state and the transmitted output is small. When the input optical power exceeds PT f, a transition is made to a resonance state, and the optical output jumps from point A to point B and then moves to point E. The refractive index is stabilized in a resonant state by the internal optical electric field, and the transmitted light output becomes approximately constant. In this state, even if the optical input decreases,
It is maintained up to the maintenance optical power Ps, and only when it becomes lower than that does it transit to point D and return to the low transmittance state.

FIG. 2 is a block diagram of the configuration of an ultrashort optical pulse generator according to the present invention using such a nonlinear Fabry-Perot optical bistable device. 1 is a laser controlled by electrical input; 2
4 is a first nonlinear Farpry-Perot optical bistable element into which this laser output light pulse is input, 4 is a second nonlinear Farpry-Perot optical bistable element into which the transmitted light pulse of the first optical bistable element is input, and 3 is a separation element that extracts the reflected light of the second optical bistable element 4 as an output optical pulse. In other words, as shown in FIG. A full optical pulse with a sharp oscillation rise is generated.

This laser output light pulse enters the first nonlinear Fabry-Perot optical bistable element 2, and its switch threshold value FT
When it reaches , it transitions to a resonant state and rapidly turns on, producing transmitted light as shown in Figure 83. This corresponds to shaping the output light bulk of the laser 1 into a rising edge determined by the leading edge vi of the output light of the laser 1 and the turn-on time of the first optical bistable element 2. This transmitted light passes through the separation element 3 and enters the second nonlinear 7 Abry-Perot optical bistable element 4.

As shown in FIG. 3, this transmitted light waveform completely suppresses the light output in the turn-off state and further shapes the steep front. At this time, the reflectance of the nonlinear Fabry-Perot resonator makes a steep transition from high reflectance in the turned-off state to low reflectance in the turned-on state. Therefore, if the reflected light from the second optical bistable element 4 is extracted as an output optical pulse by the separation element 3, the first... An extremely short optical pulse with a pulse width d determined by the sum of the turn-on times of the second 7-applibel optical bistable elements 2 and 4 is obtained.

〔Effect of the invention〕

According to the present invention, it is possible to generate an extremely short optical pulse (about 12 Ps) which is one order of magnitude shorter than that due to mode locking of a semiconductor laser.

In this method, the rise of the electric field inside the resonator acts as positive feedback, and the finesse of the resonator lowers the threshold value, making it suitable for miniaturization.

That is, ultrashort optical pulses can be easily generated using the optical power of a semiconductor laser, making it useful as a basic pulse generator for optical computers. In particular, it is thought that the large optical nonlinearity associated with the exciton level of the superlattice and micro optical waveguide technology (optical IC technology) will enable IPs switching times to be realized with a threshold of 1 μW and a size of approximately 1 μmφ, and this will lead to future development. It is a highly sensitive means.

[Embodiment of the Invention] FIG. 4 shows the configuration of a specific embodiment of the ultrashort optical pulse generator according to the present invention. IJ is the GHA s substrate, 12
A surface-emitting type distributed feedback semiconductor laser formed on this substrate Il performs distributed feedback oscillation using a GaAs-GaAtAs black lattice. Reference numeral 13 denotes a G a AHA s barrier layer through which the output light from the laser Z 2 is transmitted without being totally absorbed, and is made incident on the first optical bistable element 14 . This first optical bistable element is a G BA s -AtA S Bragg reflector 14 .
．． Between 142 and 142: GaAs-GaA4As superlattice nonlinear medium 143 is sandwiched between the two. 〇15 is a blazed Bragg coupler as a separation element, which is 3 dB
Acts as a beam splitter. This coupler 15
The transmitted light enters the second optical bistable element I6. This second optical bistable element 16, like the first optical bistable element, is a Bragg reflector 16. ．． 16. superlattice nonlinear medium I6 between
s' (i- sandwiched configuration, its threshold power is 3 dB when the transmitted light is 3 dB at the blazed Bragg coupler 15.
is set to approximately H relative to that of the first optical bistable element, 14. The reflected light from this second optical bistable element 16 is separated by a coupler 15 and taken as an extremely short output optical pulse.

In this embodiment, by using semiconductor laser technology, it is possible to realize an optical pulse generator that is compact and can generate extremely short optical pulses with low power.

In the above embodiment, a structure in which the respective substrate elements are laminated in the thickness direction on the substrate is shown, but these may be arranged and formed on the substrate in the horizontal direction.

In addition, from the viewpoint of performance, it is desirable to use an optical surgulator metal with low attenuation as the f3 element.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the input/output characteristics of a nonlinear no-breasted optical bistable device, Fig. 2 is a diagram showing the basic configuration of the present invention, and Fig. 3 is a diagram showing the basic configuration of the present invention.
The figure is a waveform diagram for explaining the operation, and FIG. 4 is a diagram showing the configuration of an embodiment of the present description. DESCRIPTION OF SYMBOLS 1... Laser, 2... First nonlinear Fabry Bellow optical bistable element, 3... Separation element, 4... Second nonlinear Fabry Bellow optical bistable element, l)... Substrate, 12・
...Distributed feedback semiconductor laser, 13...Buffer layer,
14...first nonlinear fiber bellows optical bistable element,
I5... Blazed Bragg coupler, 16... Second
nonlinear Fabry-Perot-yt bistable element. Applicant's agent Patent attorney name Takehiko E Figure 1 Figure 2 Figure 3!

Claims (2)

[Claims] (1) A laser that generates optical pulses under electrical input control, and a first nonlinear Fabry-Perot laser that transitions to a resonant state at a predetermined threshold upon receiving the laser's output pulses.
an optical bistable element, a second nonlinear Fabry-Bello optical bistable element to which a transmitted light pulse of the optical bistable element is input and which transitions to a resonant state at a predetermined threshold; An optical pulse generator that is fully equipped with a separation element that extracts output optical pulses. (2) The separation element is the first separation element. a beam splitter provided between the second nonlinear Fabry-Bello optical bistable elements, and a threshold value for the second nonlinear Fabry-Bello optical bistable element to reach a resonance state is the beam splitter provided between the second nonlinear Fabry-Bello optical bistable elements; The optical pulse generator according to claim 1, wherein the optical pulse generator is set to about % of that of the element.