JPS6032381A - Surface light emitting semiconductor laser device - Google Patents

Abstract

PURPOSE:To enable to arbitrarily select an oscillating wavelength in a gain range readily merely by altering the thickness of a periodic structure without depending upon the length of a resonator and to enable to alter the oscillating length to some degree near the oscillating mode wavelength by forming a distributed reflecting type having a periodic structure in an at least one resonator. CONSTITUTION:A material which has a laminated photowaveguide 9 including a diffraction grating function and electro-optical effect as photowaveguide layers 7, 8 such as a semiconductor material like InP or GaAs is used. In order to alter the oscillating wavelength of the semiconductor laser, a current source 6 is modulated. The original oscillating wavelength can be sufficiently stabilized by using a stabilized constant current source as an injection current source 1 to a semiconductor laser. The oscillating wavelength fine tuning or modulating of the laser is performed by the change DELTAn of refractive index by applying an electric field to the both ends of the photowaveguide layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laser device that arbitrarily controls the oscillation wavelength of a surface-emitting semiconductor laser. A surface cleaved perpendicular to the active layer is used as a reflector of the device, and laser light is emitted in a direction along the active layer.

On the other hand, a surface emitting laser is a semiconductor laser that emits laser light perpendicular to the substrate surface, and as shown in Figure 1,
The Fabry-Perot optical resonator is configured with an epitaxial crystal surface 3 and a substrate surface 6 or both epitaxial crystal surfaces as reflecting mirror surfaces (resonator crystal surfaces).

Reference numeral 1 indicates an injected power source, and reference numeral 2 indicates an output light 14 of an active layer.

The laser in Figure 1 is (1) a single mode short cavity laser;
(Expected to be applied to 2-dimensional laser arrays, (4) MOIJ IJ thick optical integrated circuits, etc. Fabry-Perot type that does not perform normal longitudinal mode control. In semiconductor lasers, the cavity length is 200
Although it is ~300 μm, the longitudinal mode spacing is about 10 A, which is smaller than the gain spectrum, so that the influence of tuning deviation from the center of the gain is small. On the other hand, in a general cavity surface emitting laser with a resonator length of about 10 μm that does not perform longitudinal mode control, the longitudinal mode spacing is as wide as 400 A, and the difference h between the peak wavelength of the gain spectrum and the resonance wavelength cannot be ignored. , in the worst case, it may not oscillate.

Purpose of the Invention - Conventional surface-emitting semiconductor lasers have had problems in improving fractionation because the oscillation mode wavelength is highly dependent on the resonator length. However, if at least one of the resonators is a distributed reflection type with a periodic structure, the oscillation wavelength can be controlled mainly by the thickness of the periodic structure, regardless of the resonator length.
Single mode oscillation with excellent temperature stability can be achieved. In the present invention, the oscillation mode wavelength can be easily selected within the gain range by simply changing the thickness of the periodic structure, regardless of the cavity length, and the oscillation wavelength can be adjusted to a certain extent in the vicinity of the oscillation mode wavelength. It is something that can be made variable.

Structure of the Invention FIG. 2 shows a stacked periodic structure forming one end face of a resonator of a surface emitting semiconductor laser according to the invention.

The desired oscillation wavelength λ is the refractive index of each of the layers 71 and 8.

It can be designed arbitrarily by changing the thicknesses (n+, d+), (n2.d2), and by applying a stain field to each layer of the laminated structure having an electro-optic effect through the power supply unit 6, fine tuning of the oscillation wavelength or It has a configuration that enables modulation.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows an embodiment of the structure of a wavelength tunable layered distributed reflection type semiconductor laser device according to the present invention. Here, instead of the resonator 3 of the conventional surface emitting laser shown in FIG. 1, a stacked optical waveguide 9 having a diffraction grating function is provided, and each of the optical waveguide layers 7 and 8 has an electro-optic effect. It is characterized by using a material such as a semiconductor material such as InP or GaAs. The oscillation wavelength of this semiconductor laser is changed by modulating the current source 6. By using a stabilized constant current source as the current source 1 injected into the semiconductor laser, the original oscillation wavelength can be sufficiently stabilized.

Note that 2 is an output light, 4 is an active layer, and 6 is a common encoder substrate surface.

Fine tuning or modulation of the oscillation wavelength of a semiconductor laser is performed by applying an electric field to both ends of the optical waveguide layer to change the refractive index Δn. Consider a periodic structure in which optical waveguide layers 7 and 8 having an electro-optic effect are stacked alternately as shown in FIG. Let λb be the wavelength that satisfies the Bragg condition, and let the refractive index and thickness of the alternating layers 2' and 3' be (rz, d
+); (n2゜d2), and if first-order diffracted light is used, λb −・+=d+ (1) 1 ”・(−−d2(2) 2 Equation 0) 9 From Equation (2), n1d1−n2d2 The relationship (3) holds true.

Suppose now that an electric field E is applied to both ends of the optical waveguide layer.

The refractive index N+, N2 of the layer 79 layer 8 is the Pockels constant γ
1. As γ2, N1=n1+4n1' γ1E (4) N2 + n2
It can be expressed as ++n'2 r2E(5). Similarly, if the modulated wavelength is λ, the following must be satisfied: N1d1=N2d2 (8). From the above conditions, n1γ1d
1:n2γ2d2 (9). From equations (3) and (9), the equation is n1γ1-n
2γ2 (10) If the laminated optical waveguide 9 is constructed of a Pockels material that satisfies the formula (1o), the wavelength λ expressed by the formula (6)
It can be finely tuned or modulated.

Effects of the Invention As described above, the present invention provides surface-emitting semiconductor devices having the possibility of two-dimensional array formation, which are expected to play a major role in future spatial optical information, signal processing, and optical communications. Communication that makes it easy to realize stable single-longitudinal mode oscillation at a desired wavelength, that allows fine control of the oscillation wavelength by applying an electric field, and that utilizes the stable frequency of light. It can also be used in systems such as optical heterodyne detection systems.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a conventional surface emitting semiconductor laser device, Figure 2 is a schematic diagram of a conventional surface emitting semiconductor laser device;
The figure is a cross-sectional view of a stacked resonator of a laser according to an embodiment of the present invention, viewed from the side, and FIG. 3 is a schematic cross-sectional view of a surface-emitting semiconductor laser device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Stabilization constant current source, 2... Output light, 6... Modulation current source, 4... Active layer, 5
...Resonator substrate surface, 7, 8... Optical waveguide layer,
9-...Stacked resonator.

Claims (1)

[Claims] (1) A periodic structure conductor laser device in which an active layer is formed on the entire surface of a substrate, and a plurality of optical waveguide layers are laminated on the active layer. (Takumi Applying an electrical signal separate from the injected power source to the optical waveguide layer