JP2918010B2 - Laser array and diode laser application equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to time-division multiplexed diode lasers and their various applications, especially in the fields of optical communications, optical parallelism, optical sampling, and electron beam emission from a cathode source.

[0002]

2. Description of the Related Art In time division multiplexing, a plurality of pulse output signals having the same frequency, each having a different time slot, are supplied. In conventional electronic signal time division multiplexing, electronic means is used to introduce different time slots into a plurality of pulse output signals. However, in optical communication systems, to date, a single source output pulse has been split and a time delay has been introduced into each of the split pulse sources via an optical waveguide used to transmit the split signal. Has caused time division multiplexing. This technique is somewhat cumbersome.

[0003] Diode lasers provide a compact laser source suitable for a wide range of applications. It is well known that the signal frequency response of diode lasers is small, and that there are frequencies that resonate depending on the size of the diode cavity. This resonance occurs at very high frequencies. Diode lasers that are operated to provide such a pulsed beam are known as mode-locked diode lasers. Figure 1 shows a cavity length of 4 mm
3 schematically shows the signal response of the diode laser of FIG. As seen in FIG. 1, the small signal response decreases rapidly at several gigahertz. However, there is a resonance peak at 10 GHz. The frequency of the resonance peak is related to the round trip distance of the laser cavity and therefore depends on its cavity length.

In recent years, a monolithic mode-locked diode laser has been developed by using a split contact Fabry-Perot laser that modulates at the optical resonance frequency. FIG. 5 shows a perspective view of a portion of a typical example of a system made of one material for a double heterostructure diode laser 70. Diode laser 7
An n-type ohmic contact 74 is formed on one side surface of the n ⁺ -GaAs substrate 72 of No. 0. A laminated structure is formed on the other side surface of the substrate. The laminated structure includes an n-type AlGaAs first cladding layer 76, a GaAs active layer 78,
And a p-type AlGaAs second cladding layer 80. Second
On the cladding layer 80, a p-type ohmic contact 82 is formed. As can be seen in FIG. 5, the second cladding layer 82 has a central ridge 84 extending in the longitudinal direction, the central ridge 84 directing light generation to the central region 8 in the active layer 78.
6 and is useful for exciting light to propagate in the vertical direction XX, instead of diffusing light over the entire surface of the active layer 78.

[0005] Other structures are well known, such as isolated confinement heterostructures. In a separate confinement heterostructure, two different cladding layers are provided, one for optical confinement and one for electrical confinement. In such a structure, the active layer may be a single or multiple quantum well structure.

The illustrated p-type ohmic contact of the second cladding layer 82 includes a first contact 82a at the center, a second contact 82b at one end, and a third contact 82b at the other end.
Is divided into contact portions 82c. The first contact portion 82a defines a central gain region, the second contact portion 82b defines a radio frequency (hereinafter, referred to as rf) modulation region, and the third contact portion 82c defines an acceptable region. Limit the saturated absorption region. In a normal use of such a diode laser, a laser beam is generated in the central region 86 of the first contact portion 82a by applying an appropriate DC bias to the central first contact portion 82a. r. f. The pulse signal is supplied to the second contact portion 82
b to cause the laser to pulse at the desired subcarrier frequency. Then, a signal to be modulated to the subcarrier frequency is applied to the third contact portion 82c in the form of a negative bias prohibition pulse. Typically, a further DC bias is applied to the second contact portion 82b to lower the threshold of the laser cavity and to reduce the series resistance of the illustrated portion of the diode (ie, the electrical diode Is switched on).

[0007] In some cases, the ohmic contact of the laser may be split in several different ways. For example, in the case of passive mode lock or active mode lock without modulation, it is sufficient to divide into two contact portions.

In order to actively lock the mode of the diode laser as described above, the third contact portion 82c of the diode laser is set at the optimum resonance frequency of the diode laser cavity at a frequency of r. f. Apply a signal.

R. f. Mode-locked diode lasers that are excited in this manner to generate pulses using a drive signal are known as active mode-locked diode lasers.

On the other hand, the passive mode lock is such r. f. This is a technique for supplying a pulse output from a laser without applying an input signal.

In order to generate an output pulse in the passive mode lock, by applying a reverse bias,
In the saturable absorption region, the energy band gap at the pn junction of the entire active layer is reduced. Reducing the energy bandgap provides higher levels of energy for absorbing photons generated in the gain region of the laser. At low light intensities, full excitation to the conduction band energy level does not occur even though all light is absorbed. At higher intensities, excitation to the conduction band energy levels occurs sufficiently to saturate the absorption of light, i.e., photons are not absorbed until electrons at these conduction band energy levels return to the ground state. Pass through the substance. In these structures, the mechanism of returning from the excited state to the ground state (the depopulation mechanism) is governed not by electron-hole recombination but by drift in the reverse-biased electric field to the contacts. The former process is characterized by the speed of the drift expressed below.

Vd = με where ε is the electric field strength (Vcm− ¹ ) and μ is cm ² / Vs
Represents the electric field mobility at. With appropriate bias and material thickness (eg, 2V, 2 μm), μ = 8500 cm ² / Vs
In the case of, the value of Vd obtained for the electrons in GaAs is 8.
5, which is a 10 ⁷ cm / sec. This is faster than the saturation rate for this field strength, ie about 10 ⁷ cm / sec. Within 10 picoseconds, corners are removed from the 2 μm area. Therefore, the repetition rate of the mode-locked pulse is 100 GHz.
As long as it is later, the saturable absorption region recovers. 0.5 μm thickness (minimum thickness to contain this mode)
In the case of the optical waveguide region, a higher repetition rate is possible.

Since a pulse having a low intensity is absorbed, a more stable output can be obtained if a larger reverse bias is supplied in the saturable absorption region. However, the greater the reverse bias, the greater the absorbed laser power and the lower the pulse intensity. Therefore, in the prior art passive mode-locked diode laser,
There is a trade-off between strength and stability.

It is only recently that a stable output has been obtained in a passive mode-locked monolithic diode laser. A technique known as Colliding Pulse Mode-Locking (CPM) is used. (MC Wu et al., IEDM 1990,
See pp137-139. According to this technique, the saturable absorption region of the monolithic diode laser is located at the center of the diode cavity, thereby improving pulse shaping when two oppositely propagating pulses collide in this region.

[0015] Passive mode-locked and active mode-locked diode lasers generate output pulses at the resonant frequency of the diode laser cavity. External cavity arrangements are used to provide pulsed output at lower frequencies, for example, around 1 Giga Hz. The pulse width is typically 10 picoseconds. One side of the laser is coated with an anti-reflection coating and an external mirror is used to define the cavity. Lenses are used in the focus arrangement to ensure that light mixing does not occur from one laser strip in the array to the next. This gives 1
Repetition rates below the 0 gigahertz range are possible.

As another technique for obtaining a pulse output from a one-diode laser, gain switching is known. According to this, a diode laser emits stimulated light by an ultra-high output, high frequency pulse. A short electrical pulse excitation introduced into the diode laser causes carrier reversal, thereby causing stimulated emission. Such a pulse can be generated by applying a large amplitude sine voltage to the step recovery diode. The output pulse from the step recovery diode occurs at the frequency of the original sine signal. The output pulse width is typically on the order of 50 picoseconds to 100 picoseconds. afterwards,
These pulses are applied directly to a diode laser biased to an optimum just before the threshold of laser emission. Diode lasers typically have two repetitions of the input signal.
A pulse having a pulse width on the order of 0 picoseconds is generated. There is no dependence on cavity size as in mode-locked diode lasers. Therefore, it is flexible as to the frequency at which a particular diode laser can pulse. However, diode lasers pulsed in this manner have an upper frequency limit of the order of 1 GHz. If high frequencies or narrow pulse widths are irrelevant, a pulsed laser generated in this manner may provide the appropriate optical signal.

One area in which diode lasers can be used is in optical communications. Optical communication systems are widely used because of their relatively wide bandwidth, small size, and insensitivity to electrical interference. FIG. 6 schematically shows basic components required for an optical communication system. FIG. 7 is a schematic diagram of an optical communication system according to the second aspect of the present invention. FIG. 8 is a schematic diagram of a digital signal that can be carried by the system of FIG. The illustrated arrangement provides one-way data communication from transmitter A to receiver B. Transmitter A receives on input line 50 an electrical input signal that conveys information to be transmitted. The transmitter A also has a suitable electric drive circuit 52 for extracting a drive signal for driving the diode laser 54 from the electric input signal.

The diode laser generates light that is modulated according to the information and coupled to one end of the optical fiber transmission line 56 via the first optical connector 58. The light is sent along a transmission line 56 to receiver B, where it is applied to a suitable photodetector 62 via a second optical connector 60, where it is converted to an electrical signal. Receiving circuit 6
4 processes this signal and performs predetermined processing such as demodulation, thereby generating an output signal on an output line 66 for transmitting the transmitted information in a predetermined form. The bandwidth currently achievable with such a system is sufficient for voice and data transmission over the telephone network, for example, machine-to-machine communication over a local area network (LAN). However, the wide area comprehensive service digital network (B-IS
There is increasing interest in the potential of optical communication systems that integrate voice, data and video transmissions in local loop subscriber networks such as DN. To enable such a system to compete with conventional cable television transmission systems having gigahertz bandwidth, it is desirable to provide a bandwidth in excess of 10 gigahertz, preferably as high as 100 gigahertz. . The data bandwidth requirements for LANs, especially for application equipment that requires image transmission, are likely to increase. Thus, bands above 10 GHz may be necessary for such applications.

There is a view that conventional optical transmission systems have utilized diode lasers operating in the small signal range. In such systems, the bandwidth is limited by the falloff of the subcarrier frequency of the diode laser used to supply the optical signal. Time division multiplexing in the small signal domain has been used to provide bands on the order of gigahertz. (See US Pat. No. 4,953,156.) Higher bandwidth systems have been proposed that provide arrays containing lasers of different wavelengths. These lasers are multiplexed by using grating elements or holographic elements. However, to obtain a stable wavelength,
Special grating / laser configurations, such as distributed feedback (DFB)
Alternatively, a distributed (Bragg) reflection type (DBR) must be used, but their manufacturing costs are high. Therefore, it is desirable to provide a high bandwidth optical communication system that can be easily manufactured.

If time division multiplexing is required where the repetition rate is slow but the time slot widths are similar, an external cavity arrangement can be used. One side of the laser array is provided with an anti-reflection coating and an external mirror is used to define the cavity. Lenses are used in the focus arrangement to ensure that light mixing does not occur from one laser strip in the array to the next. This allows for repetition rates on the order of 1 GHz or less. For example, to fully utilize a band having a time slot of 10 picoseconds, 1
00 independent lasers would be required.

The second area where diode lasers are used is in optical sampling. In general, optical sampling provides information about the phenomenon being monitored by monitoring changes in incident light.

Optical sampling provides a non-perturbative means that allows the exploration of electric fields and other phenomena.

For mass production, it is particularly desirable to be able to probe integrated circuits with high temporal and spatial resolution. An external electro-optical probe provides such a non-perturbative means.

FIG. 9 shows an example of an optical sampler that uses electro-optical interaction to draw a waveform diagram on a circuit wafer. The electro-optical sampler 90 is used for the circuit wafer 9.
Find 2 The illustrated probe 94 has a small electro-optical crystal 96 as an approximate electric field sensor. The technique used to determine the waveform of this electric field takes advantage of the presence of an end electric field on the surface of a two-dimensional circuit between metallization lines at different potentials.

The electro-optical crystal 96 is of a birefringent type, and the tip of the electro-optical crystal 96 is "dipped" into an electric field.
Then, the birefringence changes. This change is due to the light beam 98
Is measured by directing a light beam 98 to the tip so that the light is reflected at the surface 100 of the electro-optic crystal 96 and detecting the polarization change of the reflected beam 102 using a polarizer / detector arrangement. . The probed electric field varies in time and space. By using the light beam reflected from the probe surface as a laser beam, about 5μ
m spatial resolution can be achieved.

A probe as described above is used to draw a picture of an entire waveform with repetitive cycles by serially sampling the electric field at a single spatial point in the waveform at different temporal locations. To capture the entire waveform, it must be sampled at many different temporal locations.

The resolution of the diagram formed by the captured waveform depends on the accuracy of the signal determined for each individual point of the waveform and on the number of sampled points. The accuracy of the individual points is affected by any noise present in the signal and the width of the pulses used for sampling. Pulse length is a factor in probe design. However, by taking many samples at the same point in the waveform, the signal-to-noise ratio (S / N ratio) can be improved. Therefore, the number of sample points required to accurately capture a waveform is a value obtained by multiplying the number of times (N) at which each point was sampled by the number of different points (P) of the sampled waveform. Since optical sampling is performed in series, the time taken to capture a waveform at the desired resolution is the number of pulse cycle repetitions times the number of captured samples (NxP). Because the waveform can vary, an excessive number of samplings may not substantially improve the resolution achieved.

If a large number of samples at a point on the waveform are required to improve the signal-to-noise ratio, the pulse frequency of the beam must be synchronized with the frequency of the waveform.
This ensures that exactly the same point of the waveform is sampled each time. To subsequently sample different points of the waveform, a phase delay is introduced into the pulsed beam. This may, for example, physically change the mirror that directs the beam to the probe surface, or
The delay is introduced by a motor driven optical delay line or is done purely by electrical means.

In the case of serial sampling, it is necessary to repeat the waveform in order to draw a complete picture of the captured waveform. Otherwise, only one point of the waveform can be determined.

The sampled waveform is repetitive,
And if there is no limit to the sampling time to draw a complete diagram of the waveform, for example, if the variation in the waveform can be ignored or if the resolution can be low, the technique of serial sampling is very suitable. It could be. However, if the time to collect data is limited and high resolution is required, or if the S / N ratio is low,
Faster mode optical sampling may be desirable. However, it is generally desirable to provide faster sampling means. In addition, meaningful diagrams of non-repetitive waveforms cannot be captured using serial sampling techniques at the currently achievable pulse frequencies. Therefore, it is desirable to provide an optical sampling technique for sampling a waveform at a higher speed.

Other devices using optical sampling techniques, such as electron microscopes, also have the problem of slow data acquisition by serial sampling.

The third area where diode lasers are used is in photolithography. Optical lithography is the most preferred lithography technique in the production of patterned layers, such as semiconductor chips, because it can be used for automation and repetition in mass production. Optical lithography techniques are usually
The mask needs to be manufactured such that the photosensitive layer becomes opaque or transparent depending on the pattern on the positioning mask between the light source and the photosensitive material. Thereafter, a duplicate of the mask is formed by etching the silicon layer. However, as the size of the semiconductor chip is reduced, the beam is dispersed by diffraction of the light beam passing through the mask, and as a result, the accuracy of the reproducing method is reduced. In such environments, e-beam or X-ray lithography techniques must be used to produce patterned silicon wafers. X-rays have a shorter wavelength than visible light and are blocked by a mask formed from a suitable material, such as a metal sheet. Thus, X-rays can be used in a manner similar to how light beams have been used. However, even with such light rays, the wavelength is limited and a smaller chip is always required in the future, so that diffraction is necessarily a problem. Since X-ray lithography is extremely expensive and is only a temporary solution to the limitations of optical lithography applications that have been achieved to date, it is imperative to find another method.

One alternative to X-ray lithography is
Electron beam lithography. Electrons have very short wavelengths and can be produced relatively inexpensively. However, electron beams cannot be selectively blocked by conventional mask materials because conventional mask materials tend to be opaque to electrons. Moreover, there is no suitable mask-forming material that is transparent to electrons. Thus, the electron beam must directly pattern the wafer on a wafer coated with an electronic resist such as polymethyl methacrylate (PMMA). This becomes a problem when it becomes necessary to mass-produce wafer pattern reproduction. To date, electron beams have been used for mass production only in one-off manufacturing of patterned wafers. This is because a single electron beam that scans the wafer surface is typically used to form the pattern. A single electron beam is preferred, although the scanning speed is slow. This is because the use of an electron beam array to form a pattern creates a number of problems. To use an electron beam array to produce a patterned wafer,
Two electron beams must be used at short distances, where the Coulomb force causes the negative charge of the electron beams to disperse the electrons.

When using a single electron beam to draw an entire pattern, a system as shown in FIG. 10 is used. An electron source 110 provides a continuous beam of electrons. The electron beam is emitted toward the vacuum chamber 112,
It is focused by the electron lens system 114 and the direction is determined. The direction of the beam is controlled by an electron lens system 114, and the electron beam draws a pattern on a wafer 116 provided with an electron beam resist 118 in a vacuum chamber 112. The scanning lens system 115 can determine the direction of the beam under computer control. Thus, the computer can be programmed to form the desired pattern. This system is ideal for producing original or individually customized chips, but is slow and too expensive to use in mass production.

Electron beam lithography also has another problem that results from a reduction in beam intensity. When electrons are continuously emitted from the electron emission surface, a cloud of electrons is inevitably formed on the surface of the electron emission device. The high charge effect in Coulomb space creates a barrier to further electron emission. Therefore, the intensity of the emitted beam is reduced.

Therefore, there is a need for an advanced lithography technique that is suitable for manufacturing small silicon chips and that can be used immediately for mass production.

The Coulomb interaction of electrons between adjacent beams limits the application of electron beams beyond electron beam lithography. For example, to date, focusing multiple electron beams into a single point to provide a high intensity electron beam that can be used in any application, including multiple types of scanning and display devices Had a problem. There is also a problem with an electron microscope that uses a single electron beam for scanning. The use of a beam array to draw diagrams faster on the surface is due to Coulomb interactions.

Therefore, there is a need for an advanced electron beam emitting device that can be used in many applications.

Light sources can also be used in the field of optical processing. In such systems, light emission from the diode laser is typically induced by electrical signals in response to stored data. At the present time, since faster processing is desired, parallel processing, that is, processing that causes more than one event in one clock cycle of the processing device, is increasingly desired.

Optical processing allows for a dramatic increase in the processing speed in question, and parallel processing can further increase the speed at which the functions of the processing unit are performed on the data.

A typical parallel processing device includes a light source array connected via a lens system to a modulator provided on the image plane of the lens system. The modulator takes the form of a two-dimensional array, performing a plurality of operations simultaneously at a plurality of outputs of the light source array. The output of the light source resulting from the operation performed on the laser light input to the modulator is connected to the detector array via a second lens system. Since the optical parallel processing device has a large system, it may be difficult to design the device, and it cannot be downsized.

[0042]

As described above, in a diode laser, a pulse having a small intensity is absorbed. Therefore, if a larger reverse bias is supplied in the saturable absorption region, a more stable output can be obtained. Is obtained. However, the greater the reverse bias, the greater the absorbed laser power and the lower the pulse intensity. Therefore, in the prior art passive mode-locked diode laser, there is a trade-off between intensity and stability. Diode lasers typically generate pulses having a pulse width on the order of 20 picoseconds at the repetition rate of the input signal. There is no dependence on cavity size as in mode-locked diode lasers. therefore,
It is flexible as to the frequency at which a particular diode laser can pulse. However, diode lasers pulsed in this manner have an upper frequency limit of the order of 1 GHz.

It is an object of the present invention to alleviate at least some of the above problems. As noted above, higher bandwidth systems have been proposed in optical communication systems that provide arrays containing lasers of different wavelengths. These lasers are multiplexed by using grating elements or holographic elements. However, to obtain stable wavelengths, special grating / laser configurations, such as distributed feedback (DFB) or distributed (Bragg) reflection (DBR), must be used, but their manufacturing costs are high. . Therefore, it is desirable to provide a high bandwidth optical communication system that can be easily manufactured.

It is a further object of the present invention to mitigate at least some of the above problems associated with conventional optical communication systems.

As described above, in the optical sampling system, the time for collecting data is limited, and
If high resolution is needed, or if the S / N ratio is low, faster mode optical sampling may be desirable. However, it is generally desirable to provide faster sampling means. In addition, meaningful diagrams of non-repetitive waveforms cannot be captured using serial sampling techniques at the currently achievable pulse frequencies. Therefore, it is desirable to provide an optical sampling technique for sampling a waveform at a higher speed. Other devices that use optical sampling techniques, such as electron microscopes, also have the problem of slow data capture by serial sampling.

It is a further object of the present invention to mitigate at least some of the above problems associated with conventional optical sampling systems. As described above, in a lithographic apparatus, a conventional mask material tends to be opaque to electrons, so that the electron beam cannot be selectively blocked by the conventional mask material. Moreover, there is no suitable mask-forming material that is transparent to electrons.
Therefore, the electron beam must directly pattern the wafer on a wafer coated with an electronic resist such as PMMA. This becomes a problem when it becomes necessary to mass-produce wafer pattern reproduction. This computerized system in an electron beam lithography apparatus is ideal for producing original or individually customized chips, but is slow and too expensive for mass production. Further, in electron beam lithography, an advanced lithography technique which is suitable for manufacturing a small silicon chip and can be used immediately for mass production is required.

It is a further object of the present invention to mitigate at least some of the above problems associated with electron beam emission, especially in the field of photolithography. A further object of the invention is that it can be used for many application devices,
Advanced electron beam emitting device, and easy to design,
An object of the present invention is to provide a small and sophisticated optical parallel processing device.

[0048]

According to a first aspect of the present invention, a plurality of diode lasers for generating a pulse output having substantially the same frequency in response to a first input signal having substantially the same frequency are provided . and means for supplying a second input signal to each of the diode lasers of the plurality of, in order to allocate each time slot to output pulses from each of the diode laser in a pulse frequency cycles of the pulse output,
Distance traveled by the second input signals between each of the means and the plurality of diode lasers for supplying the second input signal is different
As such, the laser array including means for connecting the means for supplying the second input signal to each of the plurality of diode lasers, a is supplied.

[0049] In one preferred embodiment, the plurality of diode lasers comprises a plurality of mode-locked diode lasers. In this case, the input signal may be substantially a sinusoidal radio frequency (rf) signal. The frequency of the pulse output may be the resonant frequency of the diode cavity, or may comprise an external cavity. In the latter case, the frequency of the pulse output is the resonance frequency of the external cavity. Under these conditions, r. f. The frequency of the input signal is substantially the frequency of the resonance frequency of the external cavity.

[0050] In another preferred embodiment, the plurality of diode lasers comprises a plurality of gain-switched diode lasers. In this case, the input signal may be a short electrical pulse excitation. In this case, the frequency of the pulse output is determined by the frequency of the input signal. The pulse duration for outputting a pulsed output beam from a mode-locked diode laser is typically less than 1/10 of the cycle time. For a typical photon lifetime related to the number of round trips in the cavity before a particular photon in a pulse is emitted, the frequency difference between the radio frequency signal and the resonance of the diode laser is about 1%. Can be Here, "almost the same (subs
tantially the same) "" substantially that
of) and "substantially" should be construed accordingly.

In a first embodiment of the present invention, a diode laser array is provided in an optical communication system. The optical communication system is provided with means for modulating an output pulse of each of the plurality of diode lasers to carry information for transmission in the system.

In this embodiment, the laser array is preferably an active mode-locked diode laser array, and the means for supplying the signal is r. f. Power supply.
r. f. The lines connecting the power supply to each of the diode lasers have different lengths, so that the phase of the output generated from each diode laser is relatively different.

In a second preferred embodiment of the present invention, a diode laser array is arranged to provide a plurality of pulse outputs for use with an optical sampler. Such samplers can be used, for example, to probe dynamic physical phenomena (eg, carriers in semiconductors), electrical and optical phenomena.

The optical sampler preferably has means for directing each laser beam output from the diode laser array to probe for a phenomenon under test, and a feature in each laser beam characteristic corresponding to the characteristic of the phenomenon detected. Means for detecting a change, whereby information on the phenomenon is obtained in each time slot assigned to each diode laser.

The optical sampler can be an electron optical sampler, wherein the means for detecting a change comprises a birefringent crystal and means for detecting a change in the polarity of the laser beam reflected from the crystal surface in the presence of an electric field.

The detection means is preferably a plurality of detectors each receiving an output pulse from each of the plurality of diode lasers.

In a third preferred embodiment of the present invention, the array is arranged to include means for stimulating electron emission from the photocathode.

Assigning different time slots to the laser beams output from the respective diode lasers means that adjacent beams of electrons emitted from the photocathode are shifted from one another in time. Thus, there is no dispersion of the electron beam emitted from the photocathode as a result of the Coulomb interaction between the electron beams. In addition, high-power emission from the photocathode can be achieved by pulse output.

One suitable material suitable for forming the photocathode is the commercially available material S-1, which is a composite alloy of cesium, oxygen, palladium, and silver.

An apparatus for stimulating electron emission from a photocathode can be used in electron beam lithography. This apparatus for electron beam lithography is preferably
A mask for selectively blocking the passage of light is provided between the laser array and the photocathode, which enhances electron emission from the photocathode according to the pattern of the mask.

The means for inducing electron emission can be used in an electron microscope. The device for the electron microscope preferably comprises means for detecting electrons dispersed from the surface under investigation.

[0062] In a fourth preferred embodiment, the array is arranged to provide signals for modulation in an electro-optical or optical processor.

According to a second aspect of the [0063] present invention, a plurality of active mode-locked diode laser 該Re
Each chromatography THE comprises a plurality of active mode-locked diode <br/> Doreza which generates a pulse output at substantially the same resonant frequency determined by the dimensions of the cavity of each of the diode laser, the diode laser for transmission of each or <br/> these output pulses, and means for allocating each data <br/> time slot in the resonant frequency cycle, the Times
The means for allocating a lot includes the plurality of diode lasers.
Means for supplying an input signal to each of the
Within the frequency cycle of each of the diode lasers
To assign each time slot to these output pulses
Means for supplying the input signal and the plurality of diode lasers.
The distance traveled by the input signal to each of the
Means for supplying the input signal to the plurality of diode lasers.
Means for connecting to each of the over THE, the optical transmission system having provided.

By utilizing the high-frequency pulse generated by the diode laser for carrying information, a signal having a large bandwidth for optical transmission is supplied. By time division multiplexing some such signals, the bandwidth increases proportionately. This aspect of the invention results, at least in part, in recognizing this utility of diode lasers.

Preferably, the means for allocating each time slot comprises means for supplying a signal having a frequency substantially equal to the resonance frequency of the diode laser to one of the contacts of each of the plurality of mode-locked diode lasers. At this time, the phase of the input signal differs depending on the diode laser.

The phase of the input signal in each of the plurality of active mode-locked diode lasers is r. f. R. From a frequency source to each diode laser in the array. f. It changes by changing the length of the supply line.

Preferably, the mode-locked diode laser is an active mode-locked monolithic diode laser having one split cavity contact. The metal contacts of a monolithic diode laser are split into two or three contacts.

Preferably, a DC bias is applied to the longest contact for application to the gain region of the diode laser and has an r.f. frequency substantially equal to the resonance frequency of the diode laser. f. A clock pulse signal is applied to the second contact.

The nature of the modelock can be improved by applying a reverse bias to the third split contact to apply to the saturable absorber region. Preferably, information is added to the output of each laser by selectively applying a suppression voltage to the third contact to remove the output pulse and transmit a "0". In order to transmit a "1", the suppression voltage is removed.

The speed at which the signal is applied determines the bandwidth of the system. 10 Giga Hz due to the inertia of the system
Then it seems that pulse suppression cannot occur at the pulse frequency. The system appears to require about 10 cycles for the pulse to be suppressed. Due to the high frequencies possible using mode-locked diode lasers, the reduction in bandwidth caused by inertia is compensated, at least in part, by the increase in channel frequency. By increasing the number of channels multiplexed over time, the bandwidth can be further increased. Using threshold detection (ie,
In digital systems, where the decision of whether a bit is 1 or 0 is above or below a certain threshold);
Even higher bandwidths are possible because there is no need to completely suppress the pulses.

Other means besides signal suppression may be used to apply a signal to each of the time division multiplexed carriers.

FIG. 11 is a schematic diagram of an optical sampler according to the third aspect of the present invention. According to a third aspect of the present invention,
A plurality of diode lasers that respond to an input signal having substantially the same frequency and generate a pulse output at substantially the same frequency, wherein each laser beam output from the plurality of diode lasers probes for a phenomenon under test. And a means for providing an input signal to each of the plurality of diode lasers, such that different time slots are allocated to output pulses from the diode laser within a pulse frequency cycle of the pulse output. Means for detecting changes in the characteristics of each laser beam corresponding to the characteristics of the phenomenon detected, whereby information about the phenomenon in each time slot assigned to each diode laser can be obtained. A sampling device is provided.

Preferably, the means for supplying an input signal to each of the diode lasers includes a signal source for each of the plurality of diode lasers, such that a distance traveled by the input signal between the signal source and each of the diode lasers is different. Means for connecting.

The means for detecting is preferably a plurality of detectors, each receiving an output pulse from each of the plurality of diode lasers.

According to a fourth aspect of the present invention, the pulse emission of electrons from the cathode and each of a plurality of cathode regions so close to each other that Coulomb's interaction can take place in different time slots. Means for stimulating pulsed emission from the plurality of cathode regions to occupy.

[0076] The cathode is preferably a photocathode and the means for stimulating pulsed emission is at least one pulsed laser source.

In a first embodiment of this fourth aspect, the at least one pulsed laser source is responsive to an input signal having substantially the same frequency to generate a plurality of pulse outputs having substantially the same frequency. A diode laser, means for supplying an input signal to each of the plurality of diode lasers, and the signal supply means and the plurality of means for assigning each time slot to an output pulse from each diode laser within a pulse frequency cycle of pulse output. Means for connecting said signal supply means to each of said plurality of diode lasers in such a way that the distance traveled by said input signal between each of said diode lasers is of a different length.

In one preferred embodiment, the plurality of diode lasers comprises a plurality of mode-locked diode lasers. In this case, the input signal may be substantially a sinusoidal radio frequency (rf) signal. The frequency of the pulse output may be the resonant frequency of the diode cavity, or may comprise an external cavity. In the latter case, the frequency of the pulse output is the resonance frequency of the external cavity. Under these conditions, r. f. The frequency of the input signal is substantially the frequency of the resonance frequency of the diode laser.

In another preferred embodiment, the at least one pulsed laser source comprises a plurality of gain-switched diode lasers. In this case, the input signal may be a short electrical pulse excitation. In this case, the frequency of the pulse output is determined by the frequency of the input signal.

[0080] In a second preferred embodiment of the fourth aspect, the at least one pulsed laser source comprises a plurality of independent passively mode-locked diode lasers. Passive mode-locked monolithic diode lasers have no linkage between the time slots assigned to adjacent passive mode-locked diode lasers.
With a pulse frequency of typically about 10 to 300 GHz (depending on the cavity length), and a pulse duration typically less than 1/10 of the number of round trips, the time slot distribution across the array is random. As a result, electrons are emitted from regions of the photocathode where Coulomb interactions that occur at different times tend to be performed.

In the third embodiment, at least one
Two pulsed laser sources are dispersed by passing through a diffusing screen. The screen divides the beam into a plurality of pulsed output beams that are spatially and temporally separated from one another. The pulse delay introduced by the diffusing screen results in a random component in the generated pulse output, and the emission from the photocathode can be random. Such a system operates in a manner similar to that described above in connection with a plurality of passively mode-locked diode lasers.

Electron emitting devices of the type described above further comprise means included in the electron beam lithographic apparatus for selectively blocking the emission of electrons from the photocathode according to the depicted pattern.

In this case, the means for selectively preventing the emission of electrons can be an optical mask disposed between the laser array and the photocathode.

Alternatively, the means for selectively blocking emission may be a means for selectively blocking light emission from the laser array according to a desired pattern.

Electron beam devices of the type described above further comprise means for directing electrons to a surface and detecting electrons transmitted or reflected by the surface, which are included in the configuration of the electron microscope.

An electron beam emitting device of the type described above further comprises means for concentrating pulsed emission from a plurality of photocathode regions to provide one high density beam. According to a fifth aspect of the present invention, an electron beam lithography comprising a photocathode, means for stimulating pulsed emission of electrons from the photocathode, and means for controlling emission of electrons from the photocathode according to a desired pattern An apparatus is provided.

[0087]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention are described below. Each operates by using a diode laser array arranged to generate pulses of the same frequency but of different phases. FIGS. 2-4 illustrate a diode laser array according to the present invention and r.o.d. for each diode laser in the array such that the signal phase is different upon arrival at each diode laser in the array. f. Means for supplying a signal.

FIG. 3 shows that each of the plurality of diode lasers in the array of FIG. f. FIG. 3 is a cross-sectional view of a microstrip line suitable for supplying a signal. FIG. 4 shows that a plurality of diode lasers have r. f. FIG. 3 is a schematic plan view of a plurality of microstrip lines that carry signals. This embodiment of the invention shown in FIGS. 2 to 4 is suitable for use with other embodiments of the invention described below. However, other arrangements may be used in any of the illustrated embodiments.

Each laser 10 in the array 12 shown in FIG.
A mode-locked monolithic diode laser having a split contact divided into three parts 14, 16, 18. Each diode laser has a saturable absorber and a gain region. r. f. The signal is the first contact 1
4 to the laser 10. A positive bias is applied to the gain region through a second longer contact 16. By varying the voltage supplied to the saturable absorber via the third contact 18, information can be superimposed on the output pulse from the diode laser.

In operation of this embodiment of the invention, the phases of the output pulses excited by the laser are different.
r. f. It is important that the lengths of the feed lines from the source to the plurality of diodes 10 of the array be different. In FIG. 2, this is an r.p. of 10 picoseconds between adjacent diode lasers in the array. f. Shown as a time delay in the signal. FIG. 3 shows an array of diode lasers 10.
To r. f. 1 shows a microstrip line 20 suitable for supplying signals. The microstrip line 20 includes a metal backplane 22, for example, a substrate 24 formed of GaAs, a laser region 26, and a dielectric 28. A metal line 30 is disposed on the surface of the dielectric. For metal line 30, the back metal contact is a conductive backplane and the substrate acts as a dielectric. Typically, the effective dielectric constant is about 3, so the electrical pulse velocity along the metal line 30 is about 10 ¹⁰ cm / sec. To create a time delay of about 10 picoseconds between the outputs of adjacent lasers, r. f. The difference in line length from the source to the adjacent laser is about 1 mm.

FIG. f. FIG. 3 shows an example of a feed line shape in which the lengths of the lines from the source to four adjacent diode lasers that may form part of a long array may be different from one another as needed. r. f. An input line 32 is provided, which branches into four sub-branches 34 (a)-(b). Each of the sub-branches 34 (a) to 34 (d) differs from the adjacent branch by 1 mm in length. This arrangement is suitable for providing diode laser contacts in situ.
It is particularly advantageous when a situ facet etching method is used. The microstrip 30 is then etched to give a sine shape, and the amplitude of the sine path of each microstrip line 30 is determined by the required path length. The lengths of the lines AE, BE, CE, and DE differ by 1 mm. The longest contact AE differs in length by 3 mm from the shortest contact AD. Point E ensures that no reflection occurs at point E, r.p. f. A quarter-wave coupling is provided for impedance matching between the input and the four laser feeds.

If, instead of the in-situ facet method, for example, cleavage is used to delimit the laser facets, the feed line to each diode laser may use a similar shape and the wire bond may be .
f. A connection from the end of the line to a shorter section of each diode laser may be provided.

Next, a second embodiment of the present invention will be described with reference to FIGS. Diode laser 12 shown in FIG.
Are similar to those shown in and described in connection with FIG. Here, the same reference numerals indicate the same parts. However, the array 12 of FIG. 7 is arranged to provide a plurality of data-carrying subcarriers used in an optical transmission system. Information is applied to the output of each laser by applying a large negative voltage, typically between -2V and -5V, to the third contact.

The output signal is "0" when a negative suppression voltage is applied to the third contact, and is "1" when the suppression voltage is removed. The rate at which this signal is loaded determines the overall data rate for the structure. FIG. 8 shows a digital signal that can be carried by the system of FIG. One r. f. Each diode laser 10 in the array 12 is r. f. A signal is provided. r.
f. The signal lines 20 from the clock source to the lasers 10 in the array each have a different length, thereby providing an r. f. The phase of the signal is applied to the r. f. Different from the signal phase. A diode laser with a cavity length of about 4mm will mode lock at a repetition rate of about 10 GHz. Since the output pulse from the active mode-locked diode laser is about 10 picoseconds, in order to transfer data to the optical transmission line without overlapping between channels, one pulse is required.
Zero time slots may be used. R. In adjacent diode lasers f. To provide a time delay of 10 picoseconds between signals, the difference in feed line length needs to be about 1 mm. This required time delay is provided by the lead wiring of the first embodiment shown in FIGS. Thus, if each laser can be modulated at 10 GHz, a total bandwidth of 100 GHz is possible. This may be possible if there is no need to completely suppress the pulse by using a threshold detection method. Such bandwidth allows thousands of television channels to be carried by a single optical fiber. Such bandwidth may also be used for 3D image transfer in a rural network configuration.

When an output signal is generated from the diode laser, it is input to the optical transmission medium through a suitable concentrator 22. This is preferably a single mode optical fiber to minimize diffusion. For transmission over relatively short distances (approximately 1 km), multimode optical fibers may be used instead. The signals are transmitted and arrive at a detector designed to detect the signals being carried and transmit them for demodulation. Depending on the currently available methods, 10
Diode lasers as long as 0 microns can be produced. A diode cavity of this size has a resonant frequency of about 350 GHz. The use of the high frequency channel itself creates problems in detecting the transmitted signal.
This means that currently available electronic detection devices are approximately 50 Giga H
This is because it operates only at the frequency of z. Electronic devices that enable operation at such high frequencies are at the forefront of the state of the art and are therefore expensive.

Therefore, depending on the situation, about 10 GHz
It may be desirable to generate output pulses at a frequency of Time multiplexing systems operating at such frequencies provide sufficient bandwidth for most applications and substantially improve upon conventional optical transmission systems.

However, if a bandwidth as high as 100 gigahertz is desired, "all optical" non-power is required for implementation until electronics are developed that operate to the required frequency. A method of serialization is needed. This can be done in a linear way by using directional couplers. (M. Shabeer et al., PROC ICOC, ToulonFra
nce, 1988 (SPIE vol 963). Although the high bandwidth optical transmission system according to the invention can be utilized in a number of different ways, a particularly important application is in video receiving subscriber systems. With the bandwidth of about 100 GHz allowed by the present invention, thousands of video channels can be transmitted simultaneously, allowing the receiving subscriber to detect any number of channels or to separate individual films from thousands of broadcast programs. It becomes possible to select continuously.

One time slot is allocated to the reference signal and the receiving terminal is provided with means for demodulating the signal carried by one or more specific time slots.
This allows the receiving user to be charged for a decoder that reads each signal carried by each time slot.

The system of the second embodiment of the present invention can also be used to communicate information within a local network. In this case, one or more specific time slots are allocated to each terminal constituting the network. The communication between one or more terminals may then be carried simultaneously on the transmission line.

In such a system, one time slot is allocated as a reference slot. The master clock generated by one of the nodes of the network fills this slot, the timing of all other nodes is set with respect to this reference signal, and these nodes set all time slots to the receiving reference time slot. Relative to the position.

A third embodiment of the present invention will be described with reference to FIG. In this embodiment, an array of mode-locked monolithic diodes as described in connection with FIGS. 2-5 is provided for use with an optical sampling probe. By utilizing multiple outputs within a single cycle period, the number of samples taken at a given time is a factor N greater than that possible with a conventional continuous sampler, where N is the number of diodes in the array.
Although the diode laser array of the present invention can be used to increase the sampling rate of all optical samplers, the principle will be described below in connection with the electro-optic sampling probe of FIG.

The probe shown in FIG. 11 is similar to a conventional probe in that it has an electro-optic crystal chip whose birefringence changes when affected by an electric field. An optical sampling probe according to one embodiment of the third embodiment of the present invention can be shown in FIG. An array of diode lasers 120 similar to that shown in FIG. 2 sends laser pulses at predetermined intervals through a focusing lens 122. As described above, each diode laser generates a pulse at the same frequency determined by the size of the diode laser cavity. However, for most of one cycle there is no output from the diode laser. Thus, by arranging the outputs from the various diode lasers of the array to occur sequentially within one cycle, a much larger number of samples can be taken in a given amount of time.

A series of pulses are transmitted to the surface of the probe 124 and reflected. Detector lens 126 directs each reflected pulse to detector 128 array to determine the waveform of the electric field. Each detector in the detector array is assigned to a particular diode laser and carries information on the waveform at a particular time slot of the waveform cycle. This causes each of the detector 128 arrays to appear parallel at different points in the waveform. The output pulses from adjacent diode lasers in the array are:
If the waveforms are close enough in time to provide the required resolution, and the waveform signal is large enough, the waveform may be captured in only one signal cycle. This is a significant advantage over conventional optical samplers where the waveforms need to be captured over a number of sampling cycles, because in this embodiment of the invention the light beam of the sampling probe does not need to be synchronized to the frequency of the captured waveform. It is. This can substantially reduce the required electrons in the sampling system.

However, even if the signal-to-noise ratio is not high enough to allow the waveform to be accurately captured in a single cycle, or if higher resolution is needed,
According to the optical probe 124 of the third embodiment of the present invention,
Waveforms can be captured at a faster rate than conventional optical sampling systems. If the same number of samples are taken, the time to take the sample is reduced by the number of time slots allocated within the repetition cycle. Thus, when the number of cycles is small, the variation of the waveform seems to decrease, and the resolution seems to improve. Alternatively, if samples are taken over the same time as a conventional system, the number of samples collected will be as many as the number of time slots allocated within a repetition cycle, ie, the number of diode lasers in the array. This appears to be able to achieve improved resolution and signal-to-noise ratio.

A similar improvement in signal to noise and sample rate is to use a pulsed diode array in other types of optical samplers so that each time slot is allocated within the cycle period for each diode laser in the array. This can be realized. Such light samplers may rely on changes in various different characteristics of the laser beam to provide information about physical, electrical or optical phenomena. FIG. 12 shows a fourth embodiment of the present invention.
Will be described with reference to FIG. In this embodiment, a one-dimensional array of diode lasers as described in connection with the first embodiment of the present invention is used to generate electron emission from the photocathode. Although this electron emission device can be used for many different applications, its principles are described below in connection with electron beam lithography systems.

In FIG. 12, a diode laser array 130 is provided to emit electrons from the photocathode 138. The pulsed output beam from the diode laser array passes through a collimator lens 132 to provide a parallel beam. Next, the parallel beam is applied to the optical mask 1.
34 and the reduction lens 136. The beam then passes through a light mask 134 through which the pulsed laser beam can pass.
Is incident on the photocathode 138 made of S-1 so that electron emission occurs only at the position corresponding to the portion.
Photocathode 138 is located in vacuum chamber 140,
Electrons emitted from the photocathode 138 are collected on a silicon wafer 142 coated with an electronic resist layer 144 such as PMMA.

According to the arrangement of this embodiment, the optical mask 1
34 may be used to pattern the silicon wafer using an electron beam. Multiple electron beams
Because of the emission from the photocathode 138, the throughput of such a device is much greater than a conventional single electron beam controlled by an electron lens system. However, when electrons are continuously emitted from the photocathode 138, there are two problems described in connection with the conventional device, namely, a decrease in output due to the Coulomb space charge effect, and a decrease in resolution due to the Coulomb force. Divergence of adjacent beams that causes the lack can occur.

Nonetheless, these problems can be overcome by using an array of the type described with reference to FIG. Adjacent diode lasers of the diode laser array of FIG. 12 provide pulsed output at time intervals. Therefore, each pulse of the laser light is
When the region adjacent to the photocathode 138 does not emit electrons, electrons are emitted from the photocathode 138. This ensures that no Coulomb forces are applied between the electron beams that pattern adjacent regions of the wafer so that the pattern formed by the optical mask 134 is accurately reproduced. Careful placement of the diode laser is necessary to ensure that the diode laser, which emits electrons from portions of the photocathode 138 that tend to interact through Coulomb forces, has differently assigned pulse time slots.
This means that r. f. This is achieved by placing the feed line appropriately for the diode laser. Of course, diode lasers having the same phase will not interact with the photocathode 138 through Coulomb force.
Can stimulate electron emission from the region. Thus, a diode laser array large enough to cover one dimension of the entire wafer pattern can be easily provided without interference between the beams. The array is then scanned across the photocathode 138, transferring the entire pattern to a silicon wafer.

The pulse output of photocathode 138 resulting from pulsing the diode laser to stimulate electron emission has the second advantage of reducing the enhancement of electrons near the electron emission surface of photocathode 138. As a result, the Coulomb space charge effect is reduced, and the intensity of the emitted pulse beam of electrons becomes greater than that of a continuously emitted beam. There is an optimal duty cycle at which the average power of the electron beam is maximized.

In the manufacture of on-off semiconductor wafers, it is contemplated that a single pulsed electron beam can be used in conjunction with a scanning lens arrangement to provide a useful electron beam lithography system. The pulsed laser beam stimulates the emission of electrons from the photocathode 138 and the silicon wafer 14 coated with the electron resist layer 144
2 to generate an electron beam for writing a pattern. Due to the reduced Coulomb space charge effect resulting from the generation of the pulse, the overall beam intensity can be higher than possible with a continuously emitted beam.

A diode laser 1-D array and a diode laser array for stimulating electron emission as described above are used for adjacent diode lasers that emit electrons during different time slots of a cycle containing multiple 1-D arrays. It can be two-dimensional. In a mode-locked diode laser that generates pulses at about 10 GHz, dozens of diode arrays, each with differently assigned time slots, can be provided. This can provide a sufficient number of time slots for an array of any size that is generated without causing beam interaction problems. The 2-D edge can then be used to transfer the entire mask pattern to the silicon wafer in one go.

The active mode-locked diode laser array described with reference to FIG. 2 provides a fast and effective means of producing a patterned silicon wafer, but at any suitable frequency, a laser beam or other. The same result can be obtained by generating light from the light sources in a pulse shape. Pulse arrays of light sources other than the monolithic diode lasers specifically described are also contemplated for use in this embodiment of the invention. An example of such an arrangement is:
An independent passive mode-locked diode laser array can be used. In order to promote in-phase electron emission, a sufficient distance between the diode lasers is ensured by eliminating the leakage between the diode lasers and ensuring that leakage from back reflection is prevented. The phase of the output beam of the diode laser can be random. Dozens of different time slots can be obtained within the frequency cycle of the pulse output, so that the electron beam stimulated and emitted from photocathode 138 and the other beam emitted from the proximal region of photocathode 138 There is no interaction between them.

Another approach to stimulating the random emission of electrons to avoid Coulomb interactions is to use a pulsed output from a single laser that is dispersed to pass through a diffusing screen. The diffusion screen divides the laser pulse into a plurality of pulse outputs with random time slot assignment. These outputs are used to stimulate electron emission from the photocathode 138,
It can be used as well as the random output of a passive mode-locked diode laser array.

The electron beam emitting apparatus described with reference to the electron beam lithographic apparatus of FIG. 12 can also be used to supply high intensity electron beams that can be used, for example, in scanning and photoemission applications. Any means for generating multiple pulse outputs from a photocathode having each of the above-mentioned differently assigned time slots can be used in this application. In order to form a high-intensity beam by the above-described arrangement, a lens system for focusing each of the plurality of electron beams at a single point is provided. Due to the different time slot assignments, there is no Coulomb force interaction that tends to defocus the beam.

The high intensity beams are substantially continuous, and there is also gain from each higher intensity beam that results from being pulsed to avoid Coulomb spacing charge effects. This type of high intensity electron beam can be used for any desired application.

An array of pulsed electron beams, each having a differently assigned time slot, can also provide more information by a factor equivalent to the number of diode laser arrays or the number of different regions of electron emission from photocathode 138. It can also be used to provide the advantage of getting faster to multiple electron beams used in electron microscopes.

The fifth embodiment of the present invention will be described with reference to FIG. Diode laser array 150
Provides a pulse output in the clock cycle of the optical processor. The pulse output of the diode laser array is
The data is time-division multiplexed and modulated digitally according to the data to be processed. In one particular arrangement, data carried by the signal from the diode laser array to be time division multiplexed shows vector I _i. The output from diode laser array 150 is collected through lens 152. A modulator 154, for example, an acousto-optic modulator, is provided on the focal plane of the lens 152. In this particular embodiment, modulator 154 is one-dimensional and performs a single operation on the data continuously with repetition cycles much higher than the processor clock cycle.

The output beam from each diode laser array passes through modulator 154 and acts according to the waveform applied to modulator 154. The beam passing through modulator 154 passes through lens 156 and passes through detector array 158.
Collected in. Here, each detector detects each output beam of the diode laser array.

[0119] The repetitive waveform in one embodiment indicates a vector. This is a binary detector where the detector array 158 is arranged so that, for example, only "1" is detected due to diffraction caused by the acousto-optic modulator. If the signal indicated by the output of the diode laser array is a vector and the repetitive wave input to the modulator indicates another vector, vector / vector multiplication may be achieved. By using the system of this aspect of the invention, other functions can be accomplished on data representing different entities.

Basically, by using a modulator that operates at a faster rate than the processor clock cycle, operations on multiple data elements can be accomplished within one clock cycle. Thus, the modulator may function substantially continuously so that higher order arrays that complicate the system are not required. This speeds up processing by a large number of time-division multiplexed diode lasers. In addition, if faster processing is required, a one-dimensional or two-dimensional array of modulators can be provided, with further speedup achieved by the large number of elements in the array. In this case, a large number of time division multiplexed arrays are needed to provide data to the modulator.

In an embodiment of this aspect of the invention, the frequency of the pulse output of the diode laser is not critical. Importantly, the modulator has a modulation bandwidth that is higher than the clock cycle of the processor, ie, the bandwidth of the laser. This is generally true when the modulator operates using non-carrier effects such as electro-optic modulation.

Accordingly, diode lasers other than those described in connection with the embodiment shown in FIG. 2 are contemplated.

The embodiments of the present invention described above provide practical applications to diode laser arrays arranged to generate a continuous pulse output within a pulse cycle common to each diode laser. This type of arrangement provides a wide range of applications, the specific applications of which are described above.

[0124]

According to the diode laser of the present invention, a laser source having high output intensity and output stability and suitable for a wide range of applications can be obtained. The advantages obtained by the system and the apparatus using the diode laser are as follows.

According to the optical communication system of the present invention, about 10
Optical transmission with a bandwidth of 0 giga Hz is possible, and thousands of video channels can be transmitted simultaneously. This allows the receiver to detect any number of channels and to continuously select individual programs from thousands of broadcasts.

According to the sampling probe of the present invention,
The number of electrons required in a sampling cycle can be reduced because the light beam of the sampling probe does not need to be synchronized to the frequency of the captured waveform and the waveform need not be captured over multiple sampling cycles.

According to the optical probe of the present invention, when the same number of samples are taken as before, the time for taking out samples is reduced by the number of time slots allocated within the repetition cycle. Therefore, when the number of cycles is small,
Resolution is improved. Also, if samples are taken during the same time as before, resolution and signal-to-noise ratio are improved.

According to the electron beam emitting device of the present invention, a high-intensity electron beam used for an electron microscope can be obtained.

According to the electro-optical or optical processor of the present invention, operations on a large number of data elements are performed within one clock cycle, and the processing speed of the time division multiplexed diode laser is improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the frequency response of a diode laser with a diode cavity length of about 4 mm.

FIG. 2 is a schematic diagram of an active mode-locked monolithic diode laser array.

3 is a cross-sectional view of a microstrip line suitable for providing a radio frequency signal to each of a plurality of diode lasers of the array of FIG.

FIG. 4 shows a plurality of diode lasers having r. f. FIG. 3 is a schematic plan view of a plurality of microstrip lines that carry signals.

FIG. 5 is a cross-sectional and side perspective view of one type of diode laser.

FIG. 6 is a schematic diagram of basic components of an optical communication system.

FIG. 7 is a schematic diagram of an optical communication system according to a second aspect of the present invention.

FIG. 8 is a schematic diagram of a digital signal that can be carried by the system of FIG. 7;

FIG. 9 is a schematic diagram of a known optical sampler.

FIG. 10 is a schematic view of a known electron beam lithography apparatus.

FIG. 11 is a schematic diagram of an optical sampler according to a third aspect of the present invention.

FIG. 12 is a schematic diagram of an electron beam lithography apparatus according to a fourth aspect of the present invention.

FIG. 13 is a schematic diagram of an optical parallel processor according to a fifth aspect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Diode laser 12 Array 14 Split contact 16 Split contact 18 Split contact 20 Microstrip line 22 Metal backplane 24 Substrate 26 Laser area 28 Dielectric 30 Metal line 32 RF input line 34 Sub branch

Claims (18)

(57) [Claims] 1. A plurality of diode lasers for generating a pulse output having substantially the same frequency in response to a first input signal having substantially the same frequency, and supplying a second input signal to each of the plurality of diode lasers. means for, in a pulse frequency cycles of the pulse output, in order to allocate each time slot to the output pulses from each of the diode laser, means for supplying said second input signal
Between each of the plurality of diode lasers such that the distance traveled by the said second input signal are different, comprising: means for connecting the means for supplying the second input signal to each of the plurality of diode lasers, the Laser array. 2. The laser array according to claim 1, wherein said plurality of diode lasers comprises a plurality of mode-locked diode lasers. 3. The method according to claim 1, wherein the plurality of diode lasers includes a plurality of
2. A gain switched diode laser.
3. The laser array according to claim 1. 4. A die according to claim 1, wherein
An optical communication system including an auto-array,
To carry information for transmission in optical communication systems
Modulating the output pulse of each of the plurality of diode lasers
An optical communication system further comprising: 5. A die according to claim 1, wherein
Reacts to the characteristics of the auto laser array and the probed phenomena.
Means for detecting a change in each characteristic of the laser beam;
And thereby each of the diode lasers
In each of the individually allocated time slots
To get information about the phenomena detected
Gprobe. 6. A photocathode and an electron beam from the photocathode.
4. A method according to claim 1, which stimulates the release of the drug.
A laser array for inducing electron beam emission
Device. 7. An electron beam lithography apparatus, comprising :
Electron emission from the photocathode according to a desired pattern
Claims further comprising means for selectively blocking exit.
An apparatus for inducing electron beam emission according to claim 6. 8. A means for selectively blocking emission of said electrons.
Induces electron beam emission from the photocathode
Selectively passes the light emitted from the laser.
The device of claim 7, comprising a mask for blocking.
Place. 9. A means for selectively blocking emission of said electrons.
According to the desired pattern,
Claims: Means for selectively blocking light emission
An apparatus according to claim 7. 10. An electro-optical type having a laser array.
Or an optical processor that converts the signal for modulation
4. A method as claimed in claim 1, wherein the means is arranged for supplying.
An electro-optic or a laser array comprising
Optical processor. 11. A plurality of active mode-locked diode laser, each of the laser, at approximately the same resonant frequency determined by the dimensions of each cavity of the diode laser for generating a pulse output, a plurality of and an active mode-locked diode laser at the resonant frequency cycle in the pulse output from each of the diode laser for transmission, and means for allocating each time slot, the means for allocating said time slots, Supplying an input signal to each of the plurality of diode lasers;
Means and the diode within a pulse frequency cycle of the pulse output.
The output pulse from each of the lasers to the time slot
Means for providing the input signal for allocating each of the
And the input signal between the plurality of diode lasers and
Means for supplying the input signal so that the distance traveled by the
Connecting to each of the plurality of diode lasers . 12. To carry information for transmission,
The output pulse from each of the plurality of diode lasers;
12. The apparatus according to claim 11, further comprising: means for modulating a signal.
Optical transmission system. 13. Allocating each of said time slots
Means for controlling the resonance frequency of the diode laser.
A plurality of mode-locked signals having substantially the same frequency.
Means to supply each contact of the diode laser
The phase of the input signal is
13. The light according to claim 11 or 12, wherein each is different.
Transmission system. 14. A radio frequency source (rf) from said radio frequency source (rf).
Each length up to the laser diode array is
Active mode-locked diode lasers
To provide different phases of the input signal.
The optical transmission system according to claim 13, wherein: 15. An input signal having substantially the same frequency.
In response, a pulse output of approximately the same frequency is generated.
A plurality of diode lasers, diode lasers of the plurality of
Search for phenomena under test with each laser beam output from
Of the plurality of diode lasers
Means for supplying input signals to each, and different time slots
Within the pulse frequency cycle of the pulse output.
Assigned to the output pulse from each of the diode lasers
Of the laser beam in response to the properties of the probed phenomenon.
Means for detecting a change in each characteristic.
And the tie assigned to each of the diode lasers
Get information about the phenomenon in each of the slots
Optical sampling device. 16. A signal source and each of said diode lasers.
And the distance traveled by the input signal is different between
Connecting the signal source to each of the plurality of diode lasers.
16. The light of claim 15, further comprising means for connecting.
Sampling device. 17. Receiving Coulomb interaction with the cathode
Pulses from each of the plurality of regions of the cathode in sufficiently close proximity
So that the electron emission occupies each different time slot,
A small amount to induce pulsed electron emission from multiple regions of the cathode
Means comprising at least one pulsed laser source,
The at least one pulsed laser source has substantially the same frequency;
About the same frequency in response to an input signal with a number
Have multiple diode lasers that generate pulse output
Into each of the plurality of diode lasers.
Means for supplying a force signal and a pulse frequency of the pulse output
Within a cycle, the output power from each of the diode lasers
To assign each time slot to
Between the supply means and each of the plurality of diode lasers.
So that the distance traveled by the input signal is different.
Means for connecting the signal supply means to each of the laser diodes
An electron beam emission device comprising: 18. The method according to claim 17 , wherein
A plurality of diode lasers for providing a laser output;
Within the clock cycle of the diode laser,
Assign each time slot to the output pulse from each
And a diode circuit according to the first data signal.
Means for modulating the pulse output from each of the user arrays;
Continuously output the modulated outputs of the plurality of diode lasers to a modulator
Means for supplying the modulated signal and a second
The modulated output of the diode laser in response to a data signal
And means for modulating, modulation is the diode Les chromatography
Have a bandwidth greater than the bandwidth of the output from each of the
Optical / electro-optical processor.