JPH03222383A - Semiconductor optical element - Google Patents

Abstract

PURPOSE:To obtain a semiconductor optical element which is integrated in a two-dimensional arrangement where an optical output can be efficiently taken out upward by a method wherein a part of a resonator composed of semiconductor elements which are provided with a PN junction respectively and arranged in a ring is formed of a waveguide possessed of periodic gain. CONSTITUTION:A part of a resonator composed of semiconductor elements which are provided with a PN junction respectively and arranged in a ring is formed of a waveguide 6 possessed of a periodic gain. When a power supply is connected to an electrode provided onto a P<+>-type semiconductor ohmic contact cap layer 7, the NP junction composed of an N-type semiconductor periodic region 9 and a P-type block layer 10 is reversely biased, so that a current is blocked at the P-type block layer 10, an undoped active layer 11, an N-type buffer layer 12, and an N-type semiconductor substrate 13 under the regions 9. Therefore, a current is periodically injected into the active layer 11, so that gain itself has a period. If this grating period is set as a secondary diffraction condition, an optical output can be efficiently taken out upward.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor optical device having a two-dimensional arrangement.

[Conventional technology]

FIG. 3 shows the configuration of a conventional ring laser that can be considered as a two-dimensionally arranged semiconductor optical device. In Figure 3, 1
2 is a semiconductor gain waveguide having a pn junction, 2 is an output waveguide, 3 is a corner of a reflection groove for total reflection, 4 is a reflection groove for a half mirror, and 5 is a semiconductor substrate. By passing a forward current through the semiconductor gain waveguide 1 in the semiconductor optical device configured as described above, the present optical device oscillates as a ring laser. In order to extract the optical output of the ring laser to the outside, a half mirror 4 and an output waveguide 2 shown in FIG. 3 are required.

[Problem to be solved by the invention]

However, in manufacturing the above-mentioned half-mirror, it is necessary to control the depth of the groove and determine the branching ratio.

The above control requires an etching control technique of 0.14 or less, which is very difficult to control. Furthermore, it is even more difficult to extract the light output upwards from the plane of the paper, and no suitable means has been available in the past.

SUMMARY OF THE INVENTION An object of the present invention is to obtain a semiconductor optical device integrated in a two-dimensional arrangement that can efficiently extract optical output upward.

[Means to solve the problem]

The above object is a semiconductor optical device having a pn junction,
A distant relative is achieved by configuring a part of the ring-shaped resonator as a waveguide with periodic gain.

[Effect]

FIG. 4 shows the oscillation characteristics of a ring laser configured with a grating waveguide having a diffraction grating when the refractive index has periodicity. As is well known, in FIG. 4, a stop band is formed around the Bragg frequency determined by the period of the grating, and symmetrical return loss characteristics are shown. On the other hand, the oscillation frequency of the ring laser repeatedly appears symmetrically except for the stop band under the one-phase condition.

In FIG. 4, they are indicated by black circles, and the interval between them is determined by the ring length 4L. Here, L is the length of one side of the ring-shaped waveguide forming a square, and therefore 4L represents the total length of the ring. Note that C in C/4L, which indicates the interval, indicates the speed of light in vacuum.As shown in FIG. 4, there are two oscillation frequencies at both ends of the stop band where the reflection loss is the smallest. From this, the oscillation mode is difficult to become a single mode, and moreover, it does not oscillate at the Bragg frequency, so even if the above grating is a second-order diffraction grating, the coupling efficiency will be very low, and a large optical output will not be possible in this paper. It was difficult to take it out in the upward direction.6 FIG. 5 is a diagram showing the return loss vs. frequency characteristic when the gain itself has periodicity. In this case, as pointed out by Kogelnik et al., there is no stop band and the single oscillation frequency matches the Bragg frequency (References: H, Kogelnika
nd C, V, 5hank: Journal of Applied Physics (J, Appl, Phys)
Vol.

43, No, 5. pp2327-2335.1972)
. Therefore, it goes without saying that the oscillation mode becomes a single mode, and if the grating is a second-order diffraction grating, the optical output in the upward direction can be extracted efficiently.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a semiconductor optical device according to the present invention, and FIG. 2 is a diagram showing a cross-sectional structure of a waveguide in the above embodiment. In FIG. 1, reference numeral 3 indicates a reflection groove corner for total reflection, 5 indicates a semiconductor substrate, and 6 indicates a waveguide with periodic gain. A method for manufacturing a waveguide with periodic gain in this example will be described.

In the present embodiment shown in FIG. 1, the ring-shaped resonator is formed into a square shape, but the shape of the ring-shaped resonator is not limited to the square shape, but may have other straight shapes such as a triangle shape. The action and effect are the same.

FIG. 2 is a structural cross-sectional view showing an embodiment of the above manufacturing method. In the figure, 7 is a p++ semiconductor cap layer for ohmic contact, 8 is a p-type cladding layer, 9 is an n-type semiconductor periodic region, 10 is a p-type block layer, 11 is an undoped active layer, 12 is an n-type buffer layer, Reference numeral 13 denotes an n-type semiconductor substrate, which can be realized by epitaxial growth and photolithography, similar to the manufacturing method of a normal DFB laser. Incidentally, the reflection groove 3 for total reflection is formed by dry etching using a reactive ion beam etching method.

In order to inject a forward current into the semiconductor optical device formed as described above, when a power source is connected to the electrode provided on the first layer of the p+ type semiconductor ohmic contact cab, the n type semiconductor periodic region 9 Since the np junction of the p-type blocking layer 10 is reverse biased, current is blocked under the n-type semiconductor periodic region 9. Therefore, since current is periodically injected into the undoped active layer 11, which is the active layer, the gain itself has periodicity. By setting this grating period to second-order diffraction conditions, optical output can be efficiently extracted in the upward direction as well.

〔Effect of the invention〕

As described above, the semiconductor optical device according to the present invention is a semiconductor optical device having a pn junction, and a part of the ring-shaped resonator is formed by a waveguide having periodicity of gain. It has the following effects.

i) Optical output can be efficiently extracted upward.

n) oscillates at a single frequency.

city) can be highly integrated in two dimensions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a semiconductor optical device according to the present invention, FIG. 2 is a diagram showing a cross-sectional structure of a waveguide in the above embodiment, and FIG. 3 is a diagram showing the configuration of a conventional ring laser.
Figure 4 is an explanatory diagram of oscillation characteristics when there is periodicity in the refractive index.
FIG. 5 is an explanatory diagram of oscillation characteristics when the gain has periodicity. 6... Waveguide with periodicity of gain 9... N-type semiconductor periodic region

Claims (1)

[Scope of Claims] 1. A semiconductor optical device having a pn junction, in which a part of a ring-shaped resonator is constituted by a waveguide having periodicity of gain. 2. The semiconductor optical device according to claim 1, wherein the resonator has a linear shape. 3. Claim 1, wherein the waveguide with periodicity of gain is composed of a second-order diffraction grating.
The semiconductor optical device described in .