Electron-beam excitation laser

Abstract

An electron-beam excitation laser has a laser structure with a light emitter and reflectors on one hand and an electron source on the other hand, wherein at least part of the light emitter or reflectors has a multidimensional photonic crystal structure. An electron-beam excitation laser includes an electron source emitting electrons and a laser structure consisting of a light emitter and reflectors, accelerates electrons from the electron source, and irradiates the electrons to the laser structure to emit a laser beam from the laser structure, wherein the reflectors and / or the light emitter in the laser structure are formed with multidimensional photonic crystals in which dielectrics with different dielectric constants are arrayed in a plurality of directions at periodic intervals, and one of the dielectrics with different dielectric constants may be formed with a light-emitting material.

Description

BACKGROUNG OF THE INVENTION[0001] 1. Field of the Invention[0002] The present invention relates to an electron-beam excitation laser, and more particularly, to an electron-beam excitation laser emitting light distributed from the visible region to the ultraviolet region. An electron-beam excitation laser according to the present invention can be used as a light source for a laser beam printer, an optical recorder, optical communications, a pointer, a display, and so on.[0003] 2. Related Background Art[0004] A laser consists commonly of a laser medium, a resonator including a reflector, and an excitation source. A laser medium obtains energy from an excitation source to emit light with a specific wavelength, so that a laser beam is generated in a state that allows amplification with gain. An optical resonator reflects light emitted by the laser medium to return it to the medium. The light is caused to reciprocate many times to be progressively amplified thereby cause laser oscillatio...

AI Technical Summary

Problems solved by technology

The light is caused to reciprocate many times to be progressively amplified thereby cause laser oscillation.

However, it is difficult to cause laser oscillation by current injection, using a wide-band-gap semiconductor because of its electrical characteristics, such as the fact that such a semiconductor cannot freely be doped.

(1) Conventional electron-beam excitation lasers are low in light emission efficiency and high in oscillation threshold value. Laser oscillation occurs over a wide wavelength region in various modes.

(2) When a thick reflecting layer is provided so that its side to which an electron beam is irradiated has sufficient light reflecting capability, an electron beam attenuates by the time it reaches the active layer, thus lowering light emission efficiency. To prevent such a reduction in light emission efficiency, electron-beam accelerating voltage must be increased.

(3) Because a laser structure (a semiconductor layer) is made by vapor-phase growth methods, such as MBE and CBE, the structure is costly, so that lasers using such a structure are difficult to offer at low cost.

These defects cause local disorder in the photonic crystal, so that the oscillation threshold value becomes smaller, thus easily providing laser oscillation in a single mode.

(1) Using a photonic band gap in a multidimensional photonic crystal for a reflector makes high-level light reflection and containment possible. This allows oscillation to easily occur in a single mode within a narrow frequency range and light emission anisotropy to be controlled using photonic-crystal multidimensionality.

(2) Periodically disposing a light-emitting material in a multidimensional photonic crystal increases light emission efficiency and reduces the oscillation threshold value. This is reasoned as follows. A photonic crystal allows an optical mode in which group velocity is low to be entered. Time of interaction between a material system and a radiation field is inversely proportional to group velocity. Thus a group velocity reduction is used to increase the amplification factor (O Plus E, Vol. 21, p.

(3) Introducing local disorder, that is, defects into a photonic crystal allows a mode in which light exists locally in a photonic band gap to be entered. If a light-emitting frequency is in the photonic band gap, spontaneous light emission and inductive light emission are prohibited because no optical mode in which light is emitted is available at frequencies other than frequencies in the above-described mode. Using such a photonic crystal with defects for a light emitter or a reflector causes the above-described mode to be entered, the frequency range for light emission and laser oscillation to be narrowed, and time and space coherence to be increased. This makes it easy to cause laser oscillation in a single mode at a low threshold value.

However, the crystal is difficult to produce, it does not find wide application.

Because a periodic structure several hundreds of nanometers in size needs to be formed to make a photonic crystal which emits light in the visible region, the crystal is difficult to make.

However, because these techniques pose problems of a poor yield, high cost, and so on, a spontaneously formed regular nanostructure is preferably used.

Images