JPS61206285A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To modulate beams having a plurality of wavelengths by separate currents while coupling all beams to one optical fiber by the same lens by connecting discrete electrode to each of active layers having a plurality of compositions interposed between confinement layers in a wavelength multiple distributed feedback semiconductor laser. CONSTITUTION:When the periods of diffraction gratings 2a-2c are made mutually to differ, electrons injected from electrodes 5a-5c recombine with holes injected from an electrode 5d near the interfaces in Zn diffusion regions 4 of active layers 1a-1c and beams are generated, but the wavelengths of these beams mutually differ, and several oscillating wavelength is stabilized. When the band gaps of the confinement layers 3a-3c are increased previously, the active layers 1a-1c are separated electrically, thus modulating beams by respective current, then extracting beams having each wavelength. A plurality of the active layers are laminated in the vertical direction and several light- emitting section is formed to a vertical type, the intervals of the beam spots of outgoing beams are reduced, and beams are collimated by the same lens and can be projected to the same optical fiber, thus lowering the cost of the system, then miniaturizing the system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device, and more particularly to a wavelength division distributed feedback (DFB) semiconductor laser that generates light of a plurality of wavelengths by independent current injection.

[Prior art] Figures 4 (a) and (b) are shown in, for example, Document 1 (IEICE, Institute of Electronics and Communication Engineers,
Optoelectronics Research Group Material OQE 84-78
(September 1984))
B shows a configuration diagram of a semiconductor laser, in which (1) shows an active layer made of GaIr+AsP, and (2) shows the active layer shown in FIG. 4(b).
As shown in the figure, five types of diffraction gratings (2a) to (2e) are used.
(3) is an n-Ga1nAs diffraction grating that can control the outgoing wave entry a, entry, entry C1 entry d, and entry e by changing the period by changing the pitch 1 of the diffraction grating.
P optical waveguide layer, (5) indicates an electrode.

As shown in the illustrated configuration, the Ko-B semiconductor laser having a diffraction grating (2) inside the element selectively reflects only light of a specific wavelength, and therefore can perform laser oscillation at that wavelength.

Since the diffraction gratings (2a) to (2e) have different periods, they can oscillate at different wavelengths, and furthermore, the active layer (1)'s flow injection electrode (5) can be arranged in a single space. 5-wavelength integrated DFB that can be modulated independently due to the distance between the wavelengths
Configure the laser.

In addition, Figure 5 is from Document 2 (W, T, Tsang, App
l, Phys.

Lett, , 36(6), P441.1980), in which (1a) to (ld) are n-type active layers having mutually different compositions, (3a) to (3e) is an n-type confinement layer, (4) is a P-type region in which Zn is diffused, (5a) and (5b) are electrodes, (6) is a substrate, and (8) is an insulating layer.

In this configuration, holes are emitted from the electrode (5a) and holes are emitted from the electrode (5a).
From b), electrons pass through the Zn diffusion layer (4) in the P-type region.
, the injected carriers are injected into the n-type confinement layers (3a) to (3e), and the injected carriers are separated and injected into the active layers (1a) to (1d), and are recombined to generate photons with different wavelengths. It has become.

[Problems to be Solved by the Invention] However, in the conventional wavelength-multiplexed DFB semiconductor laser having the configurations shown in FIGS. 4(a) and 4(b), each active layer (1
] are usually separated from each other by 100 gm, so it is possible to emit light of multiple wavelengths from the same chip, but since the radius of the core of an optical fiber is several tens of pm, these laser beams can be combined into one beam. Multiple optical systems are required to focus the light onto the phi/he.

On the other hand, in the conventional wavelength multiplexed semiconductor laser with the configuration shown in Figure 5, it is impossible to modulate each wavelength and length of light with separate currents compared to the configurations shown in Figures 4(a) and (b). Met.

Therefore, this invention was made to solve the above-mentioned problems with the conventional ones. It is possible to modulate light of multiple wavelengths with separate currents, and to transmit all the light through one optical fiber using the same lens. The object of the present invention is to obtain a wavelength multiplexing semiconductor laser device that can be coupled to a wavelength multiplexed semiconductor laser device.

[Means for Solving the Problems] A semiconductor laser device according to the present invention has an individual electrode connected to each of a plurality of active layers having different compositions, which are interposed between confinement layers.

[Function] The active layer in this invention is driven by separate currents,
Generate light of different wavelengths.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, (1a) to (IC) are active layers laminated vertically on the substrate (6), (2a) to (2C) are diffraction gratings, and (3a) to (3C) are separations between each active layer. Confinement layer with larger bandgap, shaded area in (4) is Zn
(5a) to (5C) are electrodes connected to the active Ji#(la) to (IC) for lateral current injection, and (5d) is connected to the P-type layer (4). This is an electrode.

In the above configuration, when the periods of the diffraction gratings (2a) to (2C) are made different from each other, the electrons injected from the electrodes (5a) to (5C) are combined with the holes injected from the electrode (5d) into the active layer. Although write coupling occurs near the interface of the Zn diffusion regions (4) of (Ia) to (1c) and light is generated, their wavelengths are different from each other, and each oscillation wavelength is stable.

If the band gap of the confinement layers (3a) to (3C) is increased, electrically active layers (1a) to (IC)
) are separated so that they can be modulated with separate currents and emit light at different wavelengths.

Therefore, a plurality of active layers are stacked vertically to make each light emitting part vertical, and the interval between the beam spots of the emitted light is set to 2, for example.
By making it as small as ~4 gm, it is possible to collimate the light with the same lens and input it into the same optical fiber, which allows the system to be coupled with the optical fiber and become inexpensive and compact.

In the above example, the diffraction gratings (2a) to (2C) are formed directly on the active layers (1a) to (Ic), but as shown in Figure S2, the diffraction gratings (2a) to (2C) are formed directly on the active layers (1a) to (lc). In addition, a guide layer (7) having a band gap (refractive index) between that of the active layer and the confinement layer may be provided, and the diffraction grating (2) may be formed on the guide layer (7).

In addition, although the period of the diffraction gratings (2a) to (2c) is changed in the above embodiment, the oscillation wavelength can be changed by changing the refractive index (band gap) of one or more of the active layer, guide layer, and confinement layer. You can change it.

Further, in the above embodiment, the confinement layers (3a) to (3c) have a uniform composition. As shown in Figure 3, by continuously changing the refractive index (referred to as GRIN-SCH), it is possible to strengthen the light confinement and reduce the distance between each beam spot (less than 2 ω). This allows light to be focused onto the same fiber using a single lens.

[Effects of the Invention] As described above, according to the present invention, light of a plurality of wavelengths can be modulated by providing individual electrodes in each active layer and injecting a lateral current, and a plurality of light emitting parts can be arranged vertically. Because of this structure, the light can be focused on the same fiber with one lens, making the system smaller and lighter, less expensive, and only requires alignment at one location.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a wavelength multiplexed DFB semiconductor laser according to one embodiment of the present invention, and FIG. 2 is a schematic diagram showing another embodiment of the present invention in which a guide layer is provided between the active layer and the diffraction grating. , FIG. 3 is a schematic diagram of the other-body laser of the present invention, and FIG. 5 is a schematic diagram of a conventional lateral current injection wavelength multiplexed semiconductor laser. In the figure, (1), (la) to (1c) are active layers. (2), (2a) to (2C) are diffraction gratings, (3),
(3a) to (3c) are confinement layers, (5) and (5a)
- (5C) are electrodes, (8) are substrates, and (7) are guide layers. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (5)

[Claims] (1) Multiple active layers stacked vertically on a substrate, a diffraction grating close to each active layer, a confinement layer with a larger band gap separating each active layer, and a confinement layer connected to each active layer. 1. A semiconductor laser device comprising a plurality of electrodes for injecting different lateral currents. (2) A guide layer having a band gap intermediate between the active layer and the confinement layer is provided on each of the active layers, and the diffraction grating is provided on each guide layer. The semiconductor laser device described. (3) The semiconductor laser device according to claim 1 or 2, wherein light of different wavelengths is generated by changing the period of each of the diffraction gratings. (4) The semiconductor according to claim 1 or 2, wherein light of different wavelengths is generated by changing the composition of at least one of the active layer, the guide layer, and the confinement layer. laser equipment. (5) The semiconductor laser device according to claim 4, wherein the composition of the confinement layer is continuously changed.