JPH06112553A - Light emitting element - Google Patents

Abstract

PURPOSE:To obtain a light emitting element having an extremely small size by providing an airtight chamber in which at least the area between a field emission electrode and counter electrode is airtightly sealed and partially emits light and a gas which is enclosed in the airtight chamber and excited by electrons. CONSTITUTION:When electrons flying out from a cathode 12 arrive at an anode 13, the electrons collide with the molecules of an enclosed gas and excite the molecules. When the excited molecules return to a thermal equilibrium state, light is emitted in the direction shown by the arrow. The emitted light is amplified by means of a resonator composed of a gate 14 also working as a lower reflecting mirror and upper reflecting mirror 16 and causes laser oscillation (induced emission). When the laser oscillation takes place, the emitted laser light becomes perpendicular (surface emission) to a substrate 11. Therefore, a light emitting element which has an extremely small size and can be used as an optical modulator and the wavelength of which can be easily shortened by changing the kind of the gas can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and particularly to the field of optoelectronics, which is used for parallel optical information processing and optical interconnection.

[0002]

2. Description of the Related Art Conventionally, as a surface emitting laser device using a semiconductor, for example, one shown in FIG. 2 is known (reference materials: Kenichi Iga, Fumio Koyama; Applied Physics 60 (1991).
2.).

Reference numeral 1 in the figure denotes an n-type InP substrate. On the back side of the substrate 1, an n-type InP layer 2 and GaInA are formed.
An sP active layer 3, a p-type InP layer 4 and a partially opened SiO ₂ film 5 are formed. A lower electrode 6 made of Au / Zn, which is electrically connected to the InP layer 4 through the opening, is formed on the back surface side of the SiO ₂ film 5. The lower electrode 6 also serves as a reflecting mirror. A ring-shaped upper electrode 7 made of Au / Sn is formed on the InP substrate 1. A reflecting mirror 8 made of Au is formed on the entire surface of the substrate 1 including the upper electrode 7.

In the laser device having such a structure, when a voltage is applied such that the upper electrode 7 is negative and the lower electrode 6 is positive, holes are formed in the active layer 3 from the p-type InP layer 4 and n-type InP layer. Electrons are injected from 2 and an inverted distribution state is formed in the active layer 3. The light emitted when the electrons and holes injected into the active layer 3 are recombined is a resonator (resonator length L = 90 μm) formed by the reflecting mirror 8 and the lower electrode 6.
m or less) and reaches laser oscillation. At this time, the emitted laser light is in the direction perpendicular to the substrate 1 (surface emission).

[0005]

However, in the conventional laser device, the cavity length is shorter than that of the ordinary laser device (the laser device emitting in the direction parallel to the substrate) (about 300 to 500 μm in the ordinary laser device). Therefore, the injection current (threshold current) required for laser oscillation becomes large. Therefore, in general, in a surface emitting laser device using a semiconductor,
A reflecting mirror having a high reflectance of 99% or more is required.

Further, since the processing capacity increases as the wavelength of the laser light used for optical information processing becomes shorter, a surface emitting laser device which can easily oscillate a short wavelength laser is desired. However, in order to shorten the wavelength in a laser device using a semiconductor, it is necessary to use a semiconductor material having a wide band gap (wide gap semiconductor). However, in wide-gap semiconductors, it is difficult to obtain the carrier concentration necessary for laser oscillation because of the large band gap. For the above reasons, it is difficult to fabricate a short wavelength surface emitting laser device used for optical information processing from a semiconductor.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a light emitting element which can be made extremely small by using a gas excited by electrons.

[0008]

The present invention provides a substrate, a field emission electrode for emitting electrons by an electric field on the substrate, and a control electrode for controlling electrons emitted from the field emission electrode or the field emission electrode. An opposing electrode is integrally formed, and an area between the field emission electrode and the opposing electrode is at least airtightly sealed, and an airtight chamber that extracts light from a part is enclosed in this airtight chamber and excited by electrons. A light-emitting element comprising: a gas. In the present invention, the gas is, for example, Ar,
_{N 2, He-Ne, He} -Cd, include at least one of Kr.

[0009]

In the present invention, the electric potential of the field emission electrode, the electric potential of the control electrode, and the electric potential of the counter electrode are set to V _C , V _G , and V _A , respectively, and a voltage is applied so that V _C <V _G <V _A. Electrons are emitted from the field emission electrode due to the electric field generated between the field emission electrode and the control electrode, and the electrons are accelerated by the electric field between the field emission electrode and the control electrode and eventually reach the counter electrode.

When the electrons fly from the field emission electrode to the counter electrode, the electrons collide with the encapsulated gas molecules to bring them into an excited state. Light is then emitted when the excited gas molecules return to thermal equilibrium. This light can be amplified by a resonator composed of, for example, a pair of reflecting mirrors, and eventually cause laser oscillation (stimulated emission). At this time, the emitted laser light is in a direction perpendicular to or parallel to the substrate. The wavelength can be easily shortened by changing the type of the enclosed gas.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIGS. 1 and 3 are explanatory views of a surface emitting gas laser device as a light emitting element according to Embodiment 1 of the present invention. FIG. 1 is a sectional view of the device and FIG. 3 is a plan view of FIG. Indicates.

Reference numeral 11 in the figure is a quartz substrate having a comb-shaped cathode 12 and an anode 13 facing each other on its upper surface. The substrate 11 corresponding to the region between the cathode 12 and the anode 13 and its periphery is etched to form a recess 11a.
Are formed. A gate (reflecting mirror) 14 is formed in the recess 11a. Here, the cathode 12,
The anode 13 and the gate 14 are collectively called a micro field emission emitter.

An airtight chamber 17 is formed by the substrate 11, the spacer 15 made of glass on the cathode 12 and the anode 13, and the reflecting mirror 16 on the spacer 15. The micro field emission emitter has a structure hermetically sealed by the airtight chamber 17. A resonator is constituted by a reflecting mirror 16 which is different from the gate 14 which also serves as the reflecting mirror. The airtight chamber 17 is filled with Ar gas, for example.
The surface emitting gas laser device having such a structure is manufactured as follows.

First, Al is vapor-deposited on a quartz substrate 11 by a vacuum vapor deposition method and then patterned to form a comb-shaped cathode 12 and an anode 13 so that they face each other as shown in FIG. Next, the cathode 12 and the anode
Using the mask 13 as a mask, a part of the surface of the substrate 11 is isotropically etched using a hydrofluoric acid-based etching solution to form a recess 11a. This produces a micro field emission emitter consisting of the cathode 12, the anode 13 and the gate. In addition,
The distance between the cathode 12 and the anode 13 is about 100 μm.

Next, after forming a mask material on the surface side of the substrate 11, Al is vacuum-deposited to form the gate 14 which also serves as a reflecting mirror. Subsequently, the mask material is removed. Subsequently, the cathode 12, the anode 13 and the reflecting mirror 16 are set to 100
A hermetically sealed chamber 17 is formed by welding while sandwiching a glass spacer 15 in Ar gas of about Torr, and a surface emitting gas laser device is manufactured. The length of the entire laser device is 1 mm and the thickness is about 0.2 mm. The operation of the surface emitting gas laser device having the above configuration is as described below.

That is, the potential of the cathode 12, the potential of the gate 14 and the potential of the anode 13 are respectively V _C , V _G and V _A, and V
_C <When a voltage is applied so as the V _G <V _A, cathode
Electrons are emitted from the cathode 12 due to the electric field generated between the gate 12 and the gate 14, and the electrons are accelerated by the electric field between the cathode 12 and the gate 14 and eventually reach the anode 13.

When the electrons fly from the cathode 12 to the anode 13, the electrons collide with the enclosed gas molecules and excite the gas molecules. Then, when the excited gas molecules return to the thermal equilibrium state, light is emitted as shown by the arrow. This light is amplified by the resonator composed of the gate 14 also serving as the lower reflecting mirror and the upper reflecting mirror 16, and eventually laser oscillation (stimulated emission) occurs. At this time, the emitted laser light is in a direction (surface emission) perpendicular to the substrate 11. Further, it is possible to easily shorten the wavelength by changing the type of the enclosed gas.

According to the surface emitting gas laser device of the above embodiment, the substrate 11 made of quartz, the gate 14 also serving as a reflecting mirror provided in the concave portion 11a of the substrate 11 and the substrate 11 facing each other are provided. Provided cathode 12 and anode 13,
The cathode 12, the anode 13 and the gate 14 are hermetically sealed, and a reflecting mirror 16 and a spacer 15 which together with the substrate form an airtight chamber 17, and Ar gas enclosed in the airtight chamber are provided. Therefore, it is possible to realize a short wavelength surface emitting laser device that can be made extremely small.

In fact, when the gate 14 of the laser device of FIG. 1 is grounded and a voltage of −80 V is applied to the cathode 12 and +100 V to the anode 13, a current of about 1 mA flows between the cathode 12 and the anode 13 and the substrate 11 And 514.5m vertically
A circular or elliptical laser light of m, about 10 mW is emitted by the cathode 12
6 pieces corresponding to the number of comb-shaped portions of were observed. (Example 2)

Referring to FIG. The surface emitting gas laser device according to the second embodiment is different from the first embodiment in that the gate also serving as the reflecting mirror is formed in the concave portion of the substrate as in the first embodiment.
The reflecting mirror 21 and the second reflecting mirror 22 are arranged parallel to the longitudinal direction of the substrate 11 to form a resonator. According to the laser device having such a configuration, circular or elliptical laser light is emitted in the direction parallel to the longitudinal direction of the substrate 11. (Embodiment 3) Referring to FIG. The surface emitting gas laser device according to the third embodiment is different from that of FIG. 1 in that a flat-plate cathode 23 is used instead of the comb-shaped cathode.

According to the laser device having the cathode 23 having such a configuration, the linear laser light is emitted in the direction perpendicular to the substrate 11. Further, when the reflecting mirror was installed as shown in FIG. 4, circular or elliptical laser light was emitted in the direction parallel to the substrate 11. (Embodiment 4) FIG. 6 shows a micro gas laser device using a conical field emission emitter according to Embodiment 4. The same members as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 31 in the figure is an n-type Si substrate. On this Si substrate 31, an insulating layer 32 made of SiO ₂ having an opening 32a is formed. A conical cathode 33 is provided in the opening 32a. This cathode 33 is
For example, it is formed by anisotropic etching using a KOH solution. A gate 34 made of W / Al also serving as a reflecting mirror is formed on the insulating layer 32. This allows the cathode
The gate 33 and the gate 34 are integrally formed on the Si substrate 31. The gate 34 is formed by a sputtering method or a vacuum evaporation method. An anode 35 also serving as a reflecting mirror is provided on the gate 34 via a glass spacer 15. Here, the spacer 15, the anode 35 and the substrate 31 constitute an airtight chamber 17.

According to the micro gas laser device having such a structure, laser characteristics similar to those of the laser device of the first embodiment can be obtained. Further, when a plurality of conical cathodes 33 are arranged as shown in FIG. 7, a plurality of laser beams can be emitted in a direction perpendicular to the substrate 31. Further, as shown in FIG. 8, when a plurality of conical cathodes 33 are arranged and a space 36 also serving as a reflecting mirror is used, a plurality of laser beams can be emitted in a direction parallel to the substrate 31. (Example 5)

FIG. 9 shows an optical modulator as a light emitting element of the present invention. In this fifth embodiment, the surface emitting gas laser devices shown in the first to fourth embodiments are connected as shown in FIG.

According to the fifth embodiment, when an electric signal is applied in the state shown in FIG. 9, the voltage between the gate and the cathode changes in conjunction with the signal voltage, and the laser oscillation output also interlocks with the signal. You can confirm that. Therefore, it was found that the surface emitting gas laser device can also be used as a light modulator.

In the above embodiments, the case where the reflecting mirror pair for the resonator is provided has been described, but the present invention is not limited to this, and the case where it is used as a light emitting element having no resonator is also included. At this time, a light-transmissive plate such as glass is provided on the light extraction side to extract light to the outside.

[0027]

As described above in detail, according to the present invention,
By using a gas excited by electrons, it is possible to provide a light emitting element which is extremely small in size, can be easily shortened in wavelength by changing the type of gas, and can be used as an optical modulator.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a surface emitting gas laser device according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a conventional surface emitting gas laser device.

FIG. 3 is a plan view of the apparatus of FIG. 1 with the upper reflecting mirror removed.

FIG. 4 is an explanatory diagram of a surface emitting gas laser device according to a second embodiment of the present invention, in which two resonators are arranged in parallel with a substrate to form a resonator.

FIG. 5 is a plan view of a main part of a surface emitting gas laser device according to a third embodiment of the present invention, which uses a flat cathode.

FIG. 6 is an explanatory view of a surface emitting gas laser device according to a fourth embodiment of the present invention, which uses a conical cathode.

FIG. 7 is an explanatory diagram of a surface emitting gas laser device according to a fifth embodiment of the present invention, in which a plurality of conical cathodes are used.

FIG. 8 is an explanatory view of a surface emitting gas laser device according to embodiment 6 of the present invention, in which a plurality of conical cathodes are used and a spacer which also serves as a reflecting mirror is used.

FIG. 9 is an explanatory diagram of an optical modulator according to the present invention.

[Explanation of symbols]

11 ... Substrate, 11a ... Recess, 12, 2
3, 33 ... Cathode, 13, 35 ... Anode, 14, 34 ...
Gate, 15, 36 ... Spacer, 16, 21, 22 ... Reflector,
17 ... Airtight chamber, 31 ... Si substrate, 32a ... Opening part.

Claims (1)

[Claims] 1. A substrate, a field emission electrode that emits electrons by an electric field on the substrate, and a control electrode that controls electrons emitted from the field emission electrode or a counter electrode that faces the field emission electrode are integrally formed. An airtight chamber which is formed and at least hermetically seals a region between the field emission electrode and the counter electrode and takes out light from a part; and a gas which is sealed in the airtight chamber and excited by electrons. Characteristic light emitting element.