JPS6057991A - Multiwavelength semiconductor laser - Google Patents

Abstract

PURPOSE:To enable to pick out the stabilized laser beams of different wavelength from the back side of a substrate in a single lateral mode and a single longitudinal mode by a method wherein a reflection coating film is formed into an array structure in the axis direction of a photo waveguide by changing the film thickness of the reflection coating film. CONSTITUTION:A stepping of refractive index is provided on both sides of an InGaAsP active layer in the direction parallel to the junction of a P type InP layer 25 and an N type InP layer 26, and the stabilization and simplification of a lateral mode of a current blocking layer is contrived. By the formation of a resonator surface 10, a resonator is divided into C1, C2 and C3, and a laser beam is picked out from the back side of a substrate. At this point, SiO2 vapor- deposited films 11a, 11b and 11c are provided, the gain of resonator interior is obtained by the reflection coating films (11a/12a) and (11b/12b), and the film thickness of Si vapor-deposited films 13a, 13b and 13c is changed, the laser beams lambda1, lambda2 and lambda3 of different wavelength can be obtained from the divided resonators C1, C2 and C3 through the reflection coating films (11c/13a), (11c/ 13b) and (11c/13c).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-wavelength semiconductor laser used as a light source in the field of optoelectronics, optical fiber communication, and the like.

Conventional configuration and its problems Conventionally, semiconductor lasers have been used for optical fiber communication4.&l l),
As v'+, light d'+' of optical information processing, optical application equipment, etc.
and 1. - (Highly anticipated and already long) P collaboration, 1-I
With the rapid improvement in performance, many of them have entered the stage of practical application, ranging from integrated semiconductor lasers to q'1. , wave j (originating) Y.

For example, an optical fiber connection (11 and :I'
In order to achieve economical reasons such as the still high price of optical fiber, and to achieve even higher capacity information transmission, multiple waves in wavelength division multiplexing communication have been adopted. 'l
'i! The realization of 'I-body 1/-the is a future challenge.

The structure of a normal semiconductor laser is 1, stable (1°7I)
Due to the demand for high voltage and low threshold current,
'l'.

In the parallel direction, there is a step in the refractive index 4 general &-J'-C
Something that improves the confinement of light within the active 171 layer? ,
1. (Use current blocking layers on both sides of '1 layer-C
'11i, I'llr, etc. are generally modified to improve confinement. In the multi-wavelength semiconductor laser, the active f1 with different bandgaps is occupied by p and me3.
Although it is sufficient to provide several layers, in a semiconductor laser having the above-mentioned structure, it is necessary to provide active layers with different band gaps in parallel in the direction parallel to the junction, and crystal growth is not possible. Therefore, the active layer with a band gap of 5゛1- must be formed in the growth direction perpendicular to the junction.
(No. 1. Figure 1 shows f + Y M (
As an example, it is a schematic cross-sectional view of 411. 3], i-board,'
, s + 6I:I cladding layer. Two laser beams with different wavelengths cause a current 11 to flow between terminals T3 and T1, and
By passing current I2 between 3-T2, InGaAs
P 1f, rll logging 1 InGaAsP taken from the second active layer 2 11 ΣrL 0 In this structure, the bandgap is 51.1. Even if it is possible to provide an ancient layer, it may be necessary to provide a step with a K MI Jji ratio on both sides of each active layer in the direction parallel to the r1 junction, or to provide a current blocking layer! 111. Therefore, is it possible to stabilize the transverse mode? , 1. It is difficult to unify the current and the threshold current to a low range. That is, conventionally -\opening is used to form -C.
The laser beam is extracted from the ζ resonator surface. In the semi-ji body 1/-. 1.1. j, l,.

There was a problem in that the provision of several active layers, stabilization and unification of transverse modes, and reduction of threshold current were not compatible.

OBJECTS OF THE INVENTION The present invention provides a multi-wavelength semiconductor 1/-zarrl! which emits laser beams of different wavelengths from the back surface of a substrate by 11'V in a stable single-transverse mode and an 11'-toe longitudinal mode. ) 4. Purpose.

Structure of the Invention This invention is based on laser) Yl gold cleavage, +: #) extraction from the formed cavity surface.
<, )Y, ;・Old Kagamiken・
Remove from the back side of the board that has been applied 1) I'f'+,
Assume that the above is an angle table of 46 degrees.
：・；(A reflective coating film is cast on the back surface of the board), and a part of the -19 wave path has a different refractive index (
+i area indication)Il'+,-・Ho1t mode 6 ・-
2. Taking advantage of the fact that the position of the gain peak changes depending on the thickness of the reflective coating film, the structure above is arrayed in the axial direction of the optical path by changing the thickness of each of the reflective coating films on the front side. In order to solve the above-mentioned problem, by creating a structure that stabilizes and unifies the transverse mode, by simply providing one more layer of active layer, laser beams of different wavelengths can be transmitted with stable rl'l- This is a multi-wavelength semiconductor laser that can be emitted from the back surface of the substrate in single-layer mode and single-longitudinal mode.

DESCRIPTION OF EMBODIMENTS The present invention will be described in detail below with reference to the drawings.

7) First, this invention has the advantage of the following two points.
l+, is there.

When a reflective coating film is provided on the surface, the original position of the gain peak, that is, the emission wavelength changes depending on the thickness of the film.

[2] Semiconductor laser (Internal-Reflection-Int.
erferenceLaser: Hereinafter abbreviated as IRI laser), a single longitudinal mode of tl, '/zi', and li2 can be obtained.

First, to explain [1], normally ゛1′1・rI
fl,1/- has a resonator surface of 1 KJ formed using cleavage, and light within the optical waveguide is reflected at the resonator surface against the air layer. At this time, the wave path is InGa
If AsP, the circle with wavelength 1.37+m has χ・j.
- has a refractive index of 3.529, and assuming that the refractive index of the air layer is equal to 1, the reflectance is approximately 31.2% (2). For example, if a SiO2 film is provided on the resonator surface, the light 5, I? Wave path V
; is the interface between the optical waveguide and the SiO2 film and S r 02
It is reflected at the interface between the film and the air layer, and a phase difference of l: occurs in the reflected light depending on the thickness of the film. As a result, the position of the original gain peak changes, that is, the emission wavelength changes. Figure 2 shows a structure in which a refractive index step and a current blocking layer are provided on both sides of the active layer in the direction parallel to the junction.
A reflective coating film made of 5in2/Au and 5jO2/84 is provided on the cavity surface of a 1.31-film m-band 1nGaAsP/InP semi-beak laser.
- Shows the relationship between and the position of the gain peak. Here, the 3102 film is used as an insulating film to prevent leakage current through Au and St. Furthermore, the refractive index of S102 for a circle with a wavelength of 1.3 μm is 1.47, and when only the 5IO2 film is provided, the reflectance is less than 20%, which is the above-mentioned 31.
Since the gain inside the resonator cannot be increased compared to 2%, one resonator surface is provided on a highly reflective Au"4:S x 02 film to achieve almost total reflection, and the other resonator surface is r [
The refractive index is almost equal to I n Ga A s P (3
, 5) Provided on the Sii 5in2 film to increase reflectance and serve as a laser beam extraction surface. Figure 2 is half 2Q
3 is a side view of the body laser 7. FIG. In this figure, the emission spectra under the following five conditions are shown in FIG.

■ No reflective coating film ■ One end surface of semiconductor 1/-the 7 VcS to2 (221
0 people) layer 8 -1, ycp, u (~3ooo A)
Form a layer 9 ■ 8102 (
KAu (up to 3000 people) layer 9, other end face K of semiconductor laser 7 5in2 (2210 people) layer 1
0'ii formation■ In addition to layers 8 and 9 K S 102 layer 10
(D, JJ S 1 (2210 people) forming layer 11■ In addition to layers 8 to 11, an additional 5t (317 people) layer 12
In Fig. 3, it is possible to shift the original gain peak (r'7 device, 289 μm) by 160 μm to 1.30571 m by changing the thickness of the reflective coating film. :l: !<i-wave 1 Its film thickness (light with a wavelength of 1.3 μm is inside S i02 1 its thickness 1) 11, the value divided by '1.47, and the final wavelength is 2
210 people) and -C depends on the phase of the reflected light at each interface, so in the case of conditions (1) and (2), the position of the gain peak hardly changes. Like this (1(
The fact that the gain peak f1't', Ii'i changes depending on the thickness of the reflective coating film is explained by providing several laser beam extraction surfaces and using reflective coating films with different thicknesses. 4. If provided, it becomes possible to emit light of multiple wavelengths from one active layer.

Next, to explain [2], in general, the longitudinal mode of a normal semiconductor laser changes depending on the temperature. --- It is easy to obtain a stable single longitudinal mode by causing so-called mode hopping from one longitudinal mode to the next longitudinal mode, but in the IRI laser, the gain spectrum obtained from the original resonator is By having two resonators that are divided into two regions with different refractive indexes and effectively combined, it becomes a divided shape with two gain peaks, each with a spectral width narrower than the original gain spectrum. have. Therefore, for each of the two gain peaks divided into n, the intensity ratio between the peak longitudinal mode and the adjacent longitudinal mode becomes larger than in the original gain peak, and since the two gain peaks are further apart, Therefore, mode hopping does not occur, and as a result, one of the gain peaks becomes dominant, resulting in a stable single-longitudinal mode.

Figure 4 (a) shows a 1.3 μm band InGaAs with a structure designed to stabilize the transverse mode similar to that used in Figure 2.
It is a P nonconductor laser 8, and a Z
A region 9 with different refractive index is provided by n diffusion, 101, cavity length L ~ 272 μm L1 ~ 1537 + m, I,
Divided into 2 to 112 μm (however, Zn diffusion region width D ~ 7 μm)
m) 1~. The frequency spectrum width (I frequency) at that time is shown below. 1. When the operating current is small, it is divided. Jl: There are two gain peaks due to the shaker; Ira no 1. However, when the operating current is increased, one becomes dominant, and the IF-[mode is achieved. Here, the interval between the two gain peaks is 64, but Ll, T, 2? i
It can be further narrowed by changing l'ir f
il: De・1 Rir. Figure 5 shows the temperature characteristics of the longitudinal mode, and the wavelength change due to el, 1 is small at 0.77/C compared to ~38/'t: in a normal semiconductor laser, and is 3o° (: The medium-longitudinal mode is achieved without mode hopping over the temperature range of Φ.
- Achieving the longitudinal mode is achieved by making it possible to achieve multiple wavelengths by using the above-mentioned reflection coding 11, etc.). One conductor relay' stand/Realization 1171
．． Meru I1-C A2. .

Based on this invention that utilizes the two points explained above (
1,371m band InGaAsP/Ink' thread - = yp
A complete diagram of the long-half 11, , , body laser is shown in Figure 6. 10
is the axial direction of the optical waveguide, which is the <011> direction.
Formed by etching with sOH solution.

11ar1. 8102 vapor deposited film, 11b, installed on both 1 and 1 o.

11 cfj mirror 1r+i 6J [3302d film deposited on the back of the polished substrate, 12a, 12bld son
Now, the Au vapor deposited films 13a and 13b are provided on the f'Lsi○2 vapor deposited films 11a and 11b.

13c is a Si vapor-deposited film provided on the St○2 vapor-deposited film 11c, and the S102 vapor-deposited film and the Au vapor-deposited film (11a/12a)
.

(11b/12b) and Sio2 vapor deposited film and Si vapor deposited u
a (11c/13a), (11c/13b), (11c
/13c) to form a reflective coating film. 14 is Z
n diffusion (a diffusion region f formed in a stripe shape in the <01〒> direction from tC, adding a region with a different refractive index of -15 to m- in the optical waveguide, and dividing the optical waveguide into lengths of β1.It2) Reflective coating film (11a/12a
).

(11b/12b), (11c/13a), (11c/
13b).

(11c/13c) and diffusion region 14 are both formed using conventional photolithography techniques. /].

Figure 7 is A of Figure 6, -A'men's rope l', (o1〒)
It is a sectional view at +1[1. 15V, [n-type TnP
), (plate, 21 is n-type InP cladding layer, 22 is InG
a8"/+"r il layer, 23 P-type InP cladding layer, 2aij P-type TnGa86P cap layer, 25 P
type InP layer, 26 &, i', +1 type InP layer. P type 1nP7%25, n]l', HIIIP layer 26
il:l 15; In the direction parallel to the joint, TnGa
By providing a step in the refractive index on both sides of the AsP story 1/1 layer 22, VC'llS', ``Stabilization of the IA4 mode as a 1jl layer'', 1. and Q'+-. Figure 8 r1 Figure 6 B-B' Gen J-Z: Straw (011)
Both 1+, ←: (within)
It shows the pattern of Y and C waves. It can be seen from Figure 8. 1: U17C, Jl, 111 (by forming the vessel surface 10 -J1, oscillator ir: 1.cl, C2, C3 are divided into individual VCs n, laser beam (l-1 taken out from the back side of the board) Here, the above 11-]iil, l
, 1111, S β02 Xiil1Q
11a, 111), provided with a film thickness of 11c% wavelength, reflective coating film (11d/12a), (11b/
In 12b), the thickness of the Si vapor deposited films 13a, 13b, and 13c was increased to 13 +-゛ for one production. zo'i1. Changing and dividing the resonator C1
, C2° C3 to reflective coating film (11c/13a
), (11C/13b), (11c/13C)'
The laser beams of different wavelengths λ1. λ2. λ3 is obtained.

Figure 9, Figure 10, each depending on the diffusion area.
(Outside; l1jlsa n, fc resonator length f!, 1~125μ
m, I! , 2-70/1m, expansion jjJl, area width d
-7 μm, S to2 vapor deposited film ~ 2210 people, A 1
1 vapor deposition film ~ 3000 people, Si vapor deposition film 71. )'1
．． 152, 316, and 4618C);n, the gain spectra and longitudinal mode temperature characteristics are shown. 10th
In the results shown in the figure, 20
In the practical hot water temperature range of approximately 46°C4 from "C4", mode hopping does not occur and three wavelengths of stable r41-longitudinal mode light emission are obtained.

This has sufficient performance for wavelength division multiplexing communication in optical fiber communication, and also has unprecedented characteristics in temperature characteristics and mode stability.

Furthermore, in the second semiconductor laser at the end of the ship, the resonator surface 10
By etching the V-shaped groove deeply enough, there is no need to use cleavage as in the conventional method when forming chips. 44”il'i&,t,b+0 of membrane
2゜Reflection from surfaces other than the back surface of the substrate, not limited to Au and Si: i −
7-, the thickness of the tung film may be controlled, and r) light,
', i' as a region 4 with different refractive index in a part of the wave 111h.
・Means for installing &)
TnP)4 may be included in the optical waveguide.

As described in detail, this invention r1
A single transverse mode is formed in the '/c direction (Y), and a resonator surface having a reflective coating film 4 on both ends of the waveguide is applied with a force 11 in the axial direction of the optical waveguide. Te lnI: Ding 4
Jlit formed at a 6° angle and mirror polished
4y! II↓ plane IL (also provided with a reflective coating film, has a resonator structure in which one laser beam is extracted from the back side of the 4Pj, and further has a structure of a Jzo1- region with a different refractive index in a part of the optical waveguide. Arraying in the axial direction of the optical waveguide by changing the thickness of the reflective coating film (/(more stable single transverse mode and single longitudinal mode with different wavelengths 157.1/-the)Y; ?i・Has the effect of being able to take out the basic IZ jj aspects.

4, Drawing No. 17i'i rl'1.1: i+7. l
! II Figure 1 1st servant r1 conventional long and half? ,! 'A cross-sectional view showing the schematic structure of an L-body laser, Figure 2 r1, a diagram showing the conditions for providing a reflective coating film provided on the same body, and Figure 3 showing the relationship between the above conditions and the position of the gain peak. Characteristic diagram, 1), Figure 4 f-hi11. ) Y, ;, 9 A region 4 with a different refractive index is provided in a part of the wave path/I, 1. , l, gain spectrum diagram of , Figure 5 t, 1 Figure 4 Temperature of longitudinal mode of semiconductor laser in VC) 1. Fig. 6 shows a Sanwa J4 'l'' which is an embodiment of the present invention.
Figure 7 of Swimming Body 1/-The 1st Celebration Map is shown in Figure 6, page 8'
A cross-sectional view along line V(:l;・Figure 8 is taken along line BB' in Figure 6
4'4'l'rke/) cross-sectional view, Fig. 9i (+ gain spectrum diagram of the three-wavelength conductor laser according to the present invention, Fig. 10 &:j: lnl 4K motor noff1i'+
1.0. '1. ＋、There is a sex diagram.

10...Approximately 4 in the axial direction of the 9-1 wave path
Angle 1 of 5°C (K ?i, tsuJl, 1lii ?:'
f, 11 a, 1 l b, 11 c --
--・-8IO2 vapor deposited film, 12a, 12b ・=-Au
Vapor deposited film, 13a, 13b, 13c...-8t vapor deposited film, 1
4・---Zn11/, 11+! Ryoui, 15-...n
type InP substrate, 21-.-=-n type InP cladding layer,
22...-InGrAsP active+'1 layer, 23...
...P-type InP cladding layer, 24 ...P-type T n
G a A.

P cap layer, 25--P-type InP layer, 26--n-type Tnl' layer.

Name of agent: Patent attorney Toshio Nakao, 1st person, 2nd person
Fig. 1 tμlη〕 ■ Dimensions Ma 2 5th Fig. -T ('(') 纺 に n- Figure 7 Fig. 8 Fig. 6O-57991 (7) Fig. 9 ■ +2Δ1C Bow IU 1 1 1 1d<°.

1 1 1 ＼ (i −= 1 o-111 Robe ,1 i　l　r　　　,,.

＼11 Be-1 snow /, 2'? ,,5 1. IJI6 1 ♂ 1゜

Claims (1)

[Claims] A resonator surface provided with an absorption-reflection coating on both ends of an internal striped optical waveguide formed by protruding a step 6 in refractive index in the direction parallel to the junction: Y;
/! + Formed at an angle of approximately 46° to the axial direction of the wave path 1
7. A coating film is also provided on the back surface of the mirror-polished substrate to create a resonator structure in which the laser beam is extracted from the back surface of the substrate. By providing regions with different refractive indexes, jli-vertical-+--F
Combine! The above-described structure is arrayed in the axial direction of the optical waveguide, the thickness of the reflective coating film of each laser is controlled, and laser beams with different wavelengths are transmitted into rL stable single-transverse mode and single-longitudinal mode. 1. Rayleigh 1
．．