JPS59201003A - Semiconductor thin film lens - Google Patents

Abstract

PURPOSE:To make a precise optical axis matching unnecessary and to simplify an adjustment of a mutual position to other optical element such as a light source, etc. by laminating two kinds of semiconductors and forming a titled lens. CONSTITUTION:A semiconductor thin film lens 10 is formed by laminating alternately a GaAs layer 12 and a Ga0.7Al0.3As layer 13 on a GaAs substrate 11. A forbidden band width, a refractive index and a thickness EgA, nA and dA, and EgB, nB and dB of the layers 12, 13 satisfy a condition of EgA<EgB, nA>nB, and the thicknesses dA, dB are made sufficiently thinner than a wavelength corresponding to the forbidden band width. Impurities of a different quantity are mixed in each semiconductor layer so that the refractive index becomes high in the center part in the direction (z), and becomes low in the substrate and the upper layer side. A light of energy being below a forbidden band width Eg of the thin film lens 10, which advances in the direction (y) is focused at some position so as to draw a sine curve in the direction (z), and an asymmetrical beam emitted from a semiconductor laser 15 can be fetched as a circular symmetrical beam 16.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film lens, particularly suitable for condensing laser light emitted from a semiconductor laser or the like.

Generally, the angle is 30° to 60° in the direction perpendicular to the light diffusing junction surface emitted from the semiconductor laser, and 4° to 10° in the parallel direction.
It is an elliptical beam with an asymmetrical angle of 0 and a large divergence angle. For this reason, for example, when a semiconductor laser is directly coupled to a rano optical beam to a leading waveguide or an optical fiber, the coupling efficiency is significantly reduced.

Therefore, a coupling system as shown in FIGS. 1(a) and 1(b) has conventionally been used. FIG. 1(a) is a schematic cross-sectional view of the coupling system (the powder is shown as a plan view). Here, the asymmetric beam 4 emitted from the semiconductor laser 1 is converted into a symmetric beam 4' by the small diameter cylindrical lens 2, and the optical fiber In addition, 5 indicates a heat sink, and 6 indicates a supporting jig. In such a coupling system, in order to obtain sufficient coupling efficiency, the optical axis of the lens and optical fiber must be aligned accurately with respect to the light beam. Must match.

However, the diameter of the aforementioned micro-diameter cylindrical lens is 0.2~
It is extremely small at 0.3 mm, and the coupling efficiency significantly decreases with respect to optical axis misalignment, so it has the disadvantage that position adjustment is extremely difficult.

SUMMARY OF THE INVENTION In view of the above drawbacks, an object of the present invention is to provide a semiconductor thin film lens that does not require highly accurate optical axis alignment and that allows easy mutual positional adjustment with optical elements such as lenses.

In the present invention, if Eg^ is the forbidden band width of semiconductor A, L^ is the same refractive index, F'g8 is the forbidden band width of semiconductor B, and nB is the same refractive index, the following condition is established: "A > rLs jEgA<Egs" The above object is achieved by a semiconductor thin film lens formed by alternately laminating semiconductors A and B that meet the above requirements.

Hereinafter, the present invention will be explained using the drawings.

FIGS. 4(a) and ('b) are schematic diagrams showing the configuration of an embodiment of the present invention, with FIG. 4(a) being a side view and FIG. 4(b) being a front view. A GaAs layer 12 with a thickness of ioo^ is formed on a GaAa substrate 11, and GaO-7Al (1
, 3A s layer 16 is formed to a thickness of 60'A. Furthermore, on top of that, G4A s layer 12 and (ErB, o, v
The AA' o and a As layers 13 are alternately laminated to have the same thickness as described above to form a semiconductor thin film lens 10 having a total thickness of several μm to more than ten μm. Here G a A s
The layer 12 and the (rao7Alo-aAs layer 16) are grown as thin film crystals using the known molecular beam epitaxial (MBE) method, vapor phase epitaxial (CVD) method, etc. The forbidden band width, refractive index, and thickness of these semiconductor layers are They are summarized in Table 1.

Table 1 The forbidden band width, refractive index, and thickness of the GaAs layer 12 are expressed as E
gA, rLA, dA and Gao, y7v! o, the forbidden band width, refractive index and thickness of the 3A6 layer 16 are respectively EgB+ r
L9. dB, the following conditions are satisfied: EgA<Egs z'rLp, >rLs. Moreover, the thickness cLA + dB of each layer is the wavelength λA (= 1.24/EgA
, unit μs, ′λs (= 1.24/Egs, unit μ
77L), it has a value of several tenths to several hundredths. In this way, dA and dB must be sufficiently thinner than λA. The forbidden band width Eg and refractive index i of the semiconductor thin film lens 10 formed by laminating these layers are approximately as follows: Eg = 1.464 (eV), 7l- = 3.5
8 is required. Therefore, the following relationship holds true between these forbidden band widths and refractive indices.

EgA<Eg<Egs, nA>n>a
s At this time, light with energy below Eg is difficult to be absorbed by the semiconductor thin film lens 10 and is transmitted.

In addition, in Figure 2 (a) and (1)), light with energy less than Eg traveling in the y direction has a sine (si) in the x direction.
n) 0 that focuses at a certain position so as to draw a curve. Therefore,
As shown in FIG. 6, an asymmetrical beam emitted from a semiconductor laser 15 is shaped by passing it through the semiconductor thin film lens 10 of the present invention, and is extracted as a circular symmetrical beam 16. There is no need for highly accurate optical axis alignment, and mutual positional adjustment of the semiconductor laser 15 and the semiconductor thin film lens 10 is easy. For that reason,
By guiding the light beam from this semiconductor thin film lens 10 to an optical fiber or a thin film optical waveguide, highly efficient optical coupling is also possible.

In the semiconductor thin film lens 10 of the above embodiment, gratings 14 are provided at both ends of the lens in order to have a lens action in the X direction as well, but if a lens action in only two directions is sufficient, the gratings 14 is not necessarily necessary.

Further, in the above embodiment, impurities were not intentionally mixed during the growth of each semiconductor layer, and no refractive index distribution was caused by the impurities. However, if the semiconductor thin film lens is doped with impurities having the distribution shown in FIG. 4(a) in two directions during growth, the refractive index is high in the center as shown in FIG. In this case, the change in the laser source in the two directions becomes more remarkable than in the previous example, and a smaller semiconductor thin film lens with a shorter lens length l can be manufactured. ), the thickness is expressed as an arbitrary scale where D is the thickness of the semiconductor thin film lens in two directions, and (S in the figure indicates the substrate portion.

Furthermore, the semiconductor thin film lens of the present invention can be constructed seven-dimensionally with a semiconductor laser. For example, as shown in FIG. 5, a normal GaAs-GaA# As semiconductor laser 25 is first fabricated on a GaA 3 substrate 21 using a mask technique, and then an rGaAs layer 2 is fabricated on the same substrate.
2, Gao, 7A10. A semiconductor thin film lens 20 is formed by stacking six layers on the aAsAs layer. In this embodiment, there is no need to adjust the positions of the semiconductor laser 25 and the semiconductor thin film lens 20, and a compact light source system that emits a symmetrical beam is constructed. Furthermore, this embodiment can be applied to integrated optical composite devices etc. by forming optical waveguides etc. in an hybrid manner on the same substrate.

In the above embodiment, GaAs and GaAlA are used as semiconductors.
Although S is used, it is also possible to construct the present invention using other ■-■ group semiconducting multi-component mixed crystals, I-Vl group semiconductors, etc.

As explained above, in the present invention, a semiconductor thin film lens is formed by laminating two types of semiconductors, so there is no need for N-tight optical axis alignment, and the mutual position *i with the optical element of the light source etc. can be easily adjusted. Ta.

[Brief explanation of the drawing]

Figure 1 (a), (b) B is a diagram showing a coupling system using a conventional micro-diameter cylindrical lens, and Figure 2 (a), (1
)) are schematic diagrams showing the configuration of the embodiments of the present invention, FIG. 6 is a perspective view showing the case where the embodiments of the present invention are used for beam shaping of a semiconductor laser, and FIGS. 4(a) and (IJ 10.20...Semiconductor Thin film lens, 11.21・
...GaAf3 substrate, 12, 22 *”ee G
aAs layer, 13, 23 e...ll11Gao, yA
Jo, sAs layer, 14... grating, 15.25... semiconductor laser. /L'J No. 4M Written amendment to the 5th hearing (voluntary) April 25, 1980 Director of the Japan Patent Office Kazuo Wakasugi 1, Indication of the case 1989 Patent Application No. 75832 2,
Title of the invention: Semiconductor thin film lens 3, relation to the case of the corrector Patent applicant Location: 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (+00) Canon Co., Ltd. 2... Convex, the specification to be amended 6, the full text of the specification to be amended is attached as a separate document). Amended Description Name of the Invention Semiconductor Thin Film Lens 2 Claims (1) 12 The forbidden band width of the semiconductor A, - is also the refraction angle B, EgA<BgB 3. Detailed Description of the Invention The present invention is In particular, the present invention relates to a thin film lens suitable for focusing laser light emitted from a semiconductor laser or the like. Generally, the light emitted from a semiconductor laser is 60° to 60° in the direction perpendicular to the junction surface, and 4° to 10° in the parallel direction.
It is an asymmetrical elliptical beam with a large divergence angle. For this reason, for example, when a light beam from a semiconductor laser is directly coupled to an optical waveguide or an optical fiber, the coupling efficiency is significantly reduced. Therefore, conventionally, a coupling system as shown in FIGS. 1(a) and 1(b) has been used. FIG. 1(a) is a schematic sectional view of the kA coupling system, and FIG. 1(b) is a plan view of the same. Here, the asymmetric beam 4 emitted from the semiconductor laser 1 is
The beam is made into a symmetrical beam 4' and introduced into the optical fiber 3. Further, 5 indicates a heat sink, and 6 indicates a support jig. In such a coupling system, in order to obtain sufficient coupling efficiency, the optical axes of the lens and the optical fiber must precisely align with the light beam. The above-mentioned small diameter cylindrical lens has a diameter of 0.2 due to the force f.
Since the coupling efficiency is extremely small at ~0.3rrKn and the optical axis misalignment decreases significantly, there is a drawback that position adjustment is extremely difficult. SUMMARY OF THE INVENTION In view of the above drawbacks, it is an object of the present invention to provide a semiconductor thin film lens that can be easily adjusted in position with respect to a semiconductor laser or other communication element. The present invention is a semiconductor that satisfies the following conditions: 3A>nB, EgA<BgB, where 12 is the forbidden band width of semiconductor A, - is the same refractive index, 1g13 is the forbidden band width of semiconductor B, and nB is the same refractive index. The above object is achieved by a semiconductor thin film lens which is made by alternately laminating semiconductors A and B, and each semiconductor layer is mixed with a different amount of impurity, and has a refractive index distribution that produces a lens effect. Hereinafter, the present invention will be explained using the drawings. 2(a) and 2(b) are schematic diagrams showing the configuration of an embodiment of the present invention, FIG. 2(a) is a side view, and the same <(b)
IF is a front view. GaAs layer 1 on QaAs substrate 11
2 with a thickness of 100A, and Ga□, 7AA'
g, 5hs Layer 16 is formed with a thickness of 30A. Furthermore, GaAs layers 12 and false o, 7 AJ□,
5hs layers 13 are alternately laminated with the same thickness as above,
A semiconductor thin film lens 10 having a total thickness of several μm to several μm is formed. Here, the GaAs layer 12 and Gao,
7 The AJO and 3AS layers 16 are grown as thin films using known molecular beam epitaxial (MBE) method, vapor phase epitaxial CCVD) method, etc. 0 The forbidden band width of these semiconductor layers,
The refractive index and thickness are summarized in Table 1. Table 1: The forbidden band width, refraction and thickness of the GaAs layer 12 are expressed as E
As gA, BA, dA, Gac7AA! o, 3AS
Let the forbidden band width, refractive index and thickness of layer 16 be EgB, respectively.
When nB and dB, the condition of Bg person'<'BgB t na > nB is satisfied. In addition, the thickness dA of each layer and the wavelength λA (-1, 24/Eg person-) corresponding to the forbidden band width, respectively, are dBfJ.
. (unit: μm), λB (-1,24/EgBs,) unit: μm), has a value of several tenths to several hundredths. In this way, dA and dB are much thinner than λA (
must not. The forbidden band width Eg and refractive index of the semiconductor thin film lens 10 formed by stacking these layers are approximately Eg-1,464 (e V ), s=3.58
Therefore, the following relationship holds true for these forbidden band widths and refractive indexes. EgA<Eg<EgB, %A>n
> rLB At this time, light with energy less than 8g is
It becomes difficult to be absorbed by the semiconductor thin film lens 10 and is transmitted through islands. Here, if different amounts of impurities (for example, 8i) are mixed into each semiconductor layer during growth and doping is performed in two directions of the semiconductor thin film lens with a distribution as shown in FIG. 4(a), the same <( As shown in b), the refractive index is high at the center and low at the substrate and upper layer sides.
In a) and (b), light with an energy of 8 g or less traveling in the X direction is focused at a position 5 so as to draw a sine curve in two directions. Therefore, as shown in FIG. 6, the asymmetrical beam emitted from the semiconductor laser 15 is shaped by passing it through the semiconductor thin film lens 10 of the present invention formed to have an appropriate lens length l, and is taken out as a circular symmetrical beam 16. Furthermore, highly accurate optical axis alignment between the light beam and the semiconductor thin film lens is possible, and mutual positional adjustment between the semiconductor laser 15 and the semiconductor thin film lens 10 is easy. Therefore, the crossed beams from this semiconductor thin film lens 10 are guided to an optical fiber or a thin film optical waveguide (thereby, highly efficient optical coupling is possible. In order to provide lens action, gratings 14 are provided at both ends of the lens, but if lens action in only two directions is sufficient, the gratings 14 are not necessarily necessary. , In (b), the thickness is expressed as an arbitrary scale where D is the thickness of the semiconductor thin film lens in two directions, and (b)
The symbol S shown in the figure refers to the substrate portion. Furthermore, the semiconductor thin film lens of the present invention can be constructed monolithically with a semiconductor laser. For example, as shown in FIG. 5, a normal GaAs-GaAfflAs semiconductor laser 25 is first fabricated on a GaAs substrate 21 using a mask technique or the like, and then a GaAs layer 22,
A semiconductor thin film lens 20 is formed by alternately stacking Ga□, 7AJ□, and 3As layers 26. In this embodiment, the mutual position adjustment of the semiconductor laser 25 and the semiconductor thin film lens 20 is easy, and a light source system that is compact and emits a symmetrical beam is constructed. Furthermore, this embodiment can be applied to integrated optical composite devices by forming optical waveguides and the like in a hybrid manner on the same substrate. In the above embodiment, GaAs and GaklA are used as semiconductors.
Although s is used, it is also possible to construct the present invention using other multi-component mixed crystals of group semiconductors or group semiconductors. Furthermore, Be or the like may be used as the impurity. As explained above, in the present invention, a semiconductor thin film lens is formed by laminating two types of semiconductors, so precise alignment of the optical axis is not required, and mutual position adjustment with optical elements such as a light source is simplified. 4. Brief explanation of the drawings Figure 1) e (b) is a diagram showing a coupling system using a conventional micro-diameter cylindrical lens, Figures 2 (a) and (b)
6 is a schematic diagram showing the configuration of an embodiment of the present invention, FIG. 6 is a perspective view showing the case where the embodiment of the present invention is used for beam shaping of a semiconductor laser, and FIGS. 4(a) and (b) are respectively A diagram showing the toping amount of impurities mixed in the semiconductor thin film lens of the example and the distribution of the refractive index, FIG. 5 is a schematic diagram showing another example of the present invention 0 10.20...Semiconductor Thin film lens, 11, 21
"-GaAs substrate, 12, 22"・GaAs layer, 13, 23"・Ga□, 7A70.3As layer, 14
,. ..., grating, 1, 5, 25... semiconductor laser.

Claims (1)

[Claims] (1) If ]lCg^ is the forbidden band width of semiconductor A, C is the same refractive index, EgB is the forbidden band width of semiconductor B, and the phase is the same refractive index, then the following condition is satisfied: nA> as * Kg^< Ega A semiconductor thin film lens made by alternately laminating semiconductors A and B at a thickness of 7 which is sufficiently thinner than the wavelength corresponding to the forbidden band width of semiconductor A.