JP2001326415A - Optical module and light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module in which the quantity of light of a radiated luminous flux can be adjusted precisely even during the scanning of a scanning line and which is small and of a simple structure, and to provide a light source device. SOLUTION: The optical module is provided with waveguides 25, 26, 27 wherein beams of incident light which are radiated from light sources 21, 22, 23 and which are incident from incident faces 25a 26a 27a are guided to outgoing faces 25b, 26b, 27b. The optical module is provided with a grating coupler 40 which is composed of a grating formed so as to be adjacent to the waveguides 25, 26, 27, and which branches the beams of incident light from the waveguides 25, 26, 27 so as to be radiated to a prescribed direction. The optical module is provided with light receiving elements 41, 42, 43 which receive the beams of light branched by the grating coupler 40 and which detect quantities of the beams of incident lights On the basis of the quantities of the beams of incident light detected by the light receiving elements 41, 42, 43, outputs of the light sources 21, 22, 23 are made variable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module and a light source device for emitting light from a light source through a waveguide, and more particularly to an optical module and a light source device capable of adjusting the output of a light source by feedback.

[0002]

2. Description of the Related Art A laser printer or a copying machine scans a light beam emitted from a light source to write on a photosensitive member. In addition, high-speed scanning can be performed by condensing a plurality of light beams at different positions in the circumferential direction or axial direction of the photoconductor. In order to emit a plurality of light beams in close proximity, the light source device has an optical module using a waveguide as shown in the plan views and side views of FIGS. 8A and 8B.

The optical module 30 has a lower cladding layer 28 formed on a substrate 24 and waveguides 25, 26, 27 formed on the lower cladding layer 28. Waveguide 25, 2
The upper portions of 6 and 27 are covered with an upper cladding layer 29. The upper cladding layer 29 and the lower cladding layer 28 have a lower refractive index than the waveguides 25, 26, and 27, confine the light beams incident from the entrance surfaces 25a, 26a, and 27a and guide them to the exit surfaces 25b, 26b, and 27b. Waves.

Light sources 21, 22, and 23 are integrally formed on a substrate 24. The light sources 21, 22, and 23 are composed of semiconductor lasers as shown in FIG. 9, and the incident surfaces 25a, 26a, and 27a of the waveguides 25, 26, and 27, respectively.
Is joined to.

In FIG. 9, a semiconductor laser substrate 12 is shown.
An active layer 14 sandwiched between a lower clad layer 13 and an upper clad layer 15 is formed thereon, and electrodes 11 and 16 are arranged on the lower surface of the substrate 12 and the upper surface of the upper clad layer 15. By applying a voltage between the electrodes 11 and 16, the light emitting points 14a and 14b (1
4a are not shown), light beams L1 and L2 are emitted.

The light beam L1 from the light emitting point 14a is
The light is emitted toward the incident surfaces 25a, 26a, and 27a of 5, 26, and 27, and is used for writing on the photoconductor. The light beam L2 emitted from the light emitting point 14b is applied to a light receiving element (not shown). The light receiving element detects the amount of light received, and based on the detection result, the control unit (not shown) controls the AP.
C (Automatic Power Control) adjustment is performed.

As a result, the driving current of the semiconductor laser is changed, and the fluctuation of the light emission intensity caused by the change of the ambient temperature of the semiconductor laser is canceled to make the light amount of the light beam emitted from the light sources 21, 22, 23 constant. . As a result, stripes and the like generated in the formed image can be prevented.

[0008]

However, according to the conventional light source device 10 described above, since the coefficients of thermal expansion of the respective components are different, if the ambient temperature fluctuates, etc., each waveguide 2
The relative positions of the light sources 5, 26, 27 and the light sources 21, 22, 23 deviate, and the coupling efficiency between the optical module 30 and the light sources 21, 22, 23 fluctuates.

APC adjustment by the control unit is performed by the light sources 21 and 2.
This is performed based on the light beam L2 emitted from the light emitting devices 2 and 23, and it is not possible to detect a change in the light amount of the light beam passing through the waveguides 25, 26 and 27 due to a change in the coupling efficiency. For this reason, the amount of light emitted from the waveguides 25, 26, and 27 cannot be made constant, and there has been a problem that a good image cannot be formed.
In addition to the case where a light source is directly coupled to the optical module 30 and the case where an optical fiber or a prism for guiding a light beam from the light source is coupled to the optical module, the same problem arises because the coupling efficiency varies.

Japanese Patent Application Laid-Open No. 9-230259 discloses a light beam writing device that detects a change in the amount of light beam by a sensor that detects synchronization for scanning a photosensitive member. However, according to this method, when irradiating the photosensitive member with a plurality of light beams, it is necessary to increase the size of the sensor by the shift of the condensing position of each light beam, and there is a problem that the light beam writing device becomes large. . Further, for example, since the light amount is detected at the head of each scanning line, there is a problem that the light amount cannot be adjusted during scanning of the scanning line.

An object of the present invention is to provide an optical module and a light source device which are capable of accurately adjusting the amount of emitted light beam even during scanning of a scanning line, and have a small and simple structure. .

[0012]

According to a first aspect of the present invention, there is provided a waveguide for guiding incident light incident from an entrance surface to an exit surface, and a waveguide formed in contact with the waveguide. A grating coupler that is formed of a grating and branches the incident light from the waveguide and emits the light in a predetermined direction; and a light receiving element that receives light branched by the grating coupler and detects the amount of light. Features.

According to this configuration, the light beam incident from the entrance surface is guided to the exit surface by the waveguide and exits. The light beam is branched in a predetermined direction by the grating coupler in the waveguide, and is received by the light receiving element to detect the amount of the branched light. By adjusting the output of the light source based on the detected light amount, it is possible to cancel the deterioration of the coupling efficiency of the light source and the optical fiber coupled to the incident surface.

According to a second aspect of the present invention, in the optical module according to the first aspect, a plurality of the waveguides are provided, and the branched light beams from the respective waveguides are emitted in different directions. Features.

According to a third aspect of the present invention, in the optical module according to the first or second aspect,
The grating of the grating coupler has a different period corresponding to each of the waveguides.

According to a fourth aspect of the present invention, in the optical module according to the first aspect, a plurality of the waveguides are provided, and the branch light from each of the waveguides is emitted in the same direction. Features.

According to a fifth aspect of the present invention, there is provided an optical module according to any one of the first to fourth aspects, a light source for irradiating the incident surface with a light beam, and a detection result of the light receiving element. And a control unit for controlling the output of the light source.

According to this structure, the light beam emitted from the light source enters from the incident surface, is guided to the emission surface by the waveguide, and is emitted as the secondary light source. Further, the light beam is branched in a predetermined direction by a grating coupler in the waveguide, and is received by a light receiving element to detect a light amount. The output of the light source is adjusted by the control unit so that the light amount of the secondary light source becomes constant based on the detected light amount.

According to a sixth aspect of the present invention, in the light source device according to the fifth aspect, the optical module and the light source are provided integrally.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. For convenience of explanation, FIGS.
The same reference numerals are given to the same parts as. FIG.
1 is a schematic perspective view showing a light beam writing device provided with a light source device of a first embodiment. The light beam writing device 1 is mounted on a laser printer, a digital copier, or the like, and can form an image.

The light source device 10 has a built-in light source.
A plurality of light beams having different light condensing positions are emitted. Light source device 1
The luminous flux emitted from 0 illuminates the polygon mirror 3 after being collimated by the collimator lens 2. The light beam reflected by the polygon mirror 3 is scanned as the polygon mirror 3 rotates. After the scanning speed is made constant by the scanning lens 4, a desired position on the photoconductor is exposed by focusing on a photoconductor (not shown), and writing is performed.

The light beam reflected by the polygon mirror 3 irradiates the reflection mirror 5 at the leading position of each scanning line. The light beam reflected by the reflecting mirror 5 is captured by the light receiving sensor 6 so that the synchronization of the plurality of light beams can be detected.

The light source device 10 has an optical module 30 as shown in the plan and side views of FIGS. 2 (a) and 2 (b). The optical module 30 has a lower cladding layer 2 on a substrate 24.
8 are formed, and the waveguides 25, 2
6, 27 are formed. The upper portions of the waveguides 25, 26, 27 are covered by an upper cladding layer 29. The upper cladding layer 29 and the lower cladding layer 28 are
The refractive index is lower than 6, 27,
Light beams incident from a, 26a, and 27a are confined and guided to emission surfaces 25b, 26b, and 27b.

A grating coupler 40 made of a grating formed at a predetermined period is provided in contact with the upper surfaces of the waveguides 25, 26, and 27. As shown in FIG. 4, the grating coupler 40 includes waveguides 25, 26,
A part of the guided light L3 passing through 27 is branched to the upper clad layer 29 side by diffraction (branched light L
4).

Assuming that the pitch of the grating L is P, the wavelength of the guided light is λ, the order of diffraction is q, and the effective refractive index of the waveguide is Neff, sin θ = Neff + qλ / P 1) It is represented by Therefore, the branch angle θ can be changed by changing the pitch P of the grating.

Further, the split light L with respect to the light quantity of the guided light L3
The light amount ratio R (hereinafter, referred to as “branch ratio”) R is represented by R = k {1−exp (−2αL)} (2) where L is the length of the grating portion. Here, k is a proportionality constant, and α is a radiation loss coefficient.

FIG. 5 shows the relationship between the radiation loss coefficient α (vertical axis) and the height H of the grating (horizontal axis). The radiation loss coefficient α changes with the height H of the grating. Therefore, by appropriately selecting the grating length L and the grating height H, the branching ratio R can be set to a desired value.

Referring to FIG. 2, light receiving elements 41, 42, 4 comprising photodiodes are provided on the upper surface of the upper cladding layer 29.
3 are provided. The light receiving elements 41, 42, and 43 are arranged corresponding to the directions of the branched light L4 branched from the waveguides 25, 26, and 27 by the grating coupler 40,
Each branch light L4 is received, and the amount of received light can be detected.

Such an optical module 30 can be manufactured by the following method. First, 7 μm of quartz is deposited on a substrate 24 made of silicon or the like while doping fluorine by CVD to form a lower cladding layer 28. Next, 5 μm of quartz is deposited by CVD without doping. After patterning into a predetermined shape by a photolithography process, reactive ion etching is performed to form waveguides 25, 26, and 27.

Next, after 0.2 μm of quartz is deposited and patterned into a predetermined grating shape by a photolithography process, a reactive ion etching process is performed to form a grating coupler 40. At this time, gratings at positions corresponding to the waveguides 25, 26, and 27 are formed with different periods. Next, quartz is deposited to a thickness of 7 μm while doping with fluorine to form an upper cladding layer 29.

Then, a material for a photodiode is deposited on the upper cladding layer 29 by CVD or the like, and after patterning, reactive ion etching is performed to form a light receiving element 4.
1, 42 and 43 are formed. Thereby, the optical module 30 can be obtained. The optical module 30 of the present embodiment obtained by the above-described manufacturing method is as follows.

Substrate material: silicon Waveguide material: quartz Effective refractive index Neff of waveguide: 1.459 Difference in refractive index between upper cladding layer, lower cladding layer and waveguide: 0.3% Waveguide cross section: 5 μm × 5 μm Grating shape: rectangular Grating height H: 0.2 μm Grating length L: 100 μm Grating period P: 0.53 μm (waveguide 25) 0.43 μm (waveguide 26) 0.37 μm (conductive) Wave 27)

Thus, the wavelength λ of the guided light L3 is 78
At 0 nm, the optical module 30 has the following characteristics. Here, the branch angle θ is set such that the direction of the exit surface is positive.

[0034]

In FIG. 2, a light source 21 is provided on a substrate 24.
22 and 23 are formed integrally with the optical module 30. The light sources 21, 22, and 23 are composed of semiconductor lasers as shown in FIG.
26, 27 are coupled to incident surfaces 25a, 26a, 27a.

FIG. 3 is a block diagram showing the configuration of the light source device 10. The light source device 10 has a control unit 31 for controlling the outputs of the light sources 21, 22, and 23. Light sources 21, 22, 2
The light beam emitted from 3 is guided by the waveguides 25, 26, and 27 and is branched by the grating coupler 40. Then, the light amounts of the respective branched lights L4 are detected by the light receiving elements 41, 42, and 43.

The results detected by the light receiving elements 41, 42, 43 are compared by the comparing section 32 with predetermined light quantity data of the branched light stored in the storage section 34. As a result of the comparison by the comparing unit 32, when the light amount of the branched light is not in the predetermined range, it is determined that the light flux of the predetermined light amount is not emitted from the optical module 30, and the driving unit 33 determines that the light sources 21, 22,
The output of the light sources 21, 22, and 23 is varied by varying the drive current of the.

When the light quantity of the branched light is within a predetermined range, the drive section 33 maintains the drive current of the light sources 21, 22, and 23. Thereby, the emission surfaces 25b, 2b of the waveguides 25, 26, 27
Adjustments are made so that a constant amount of light is always emitted from 6b and 27b.

According to the present embodiment, the waveguides 25, 26,
The waveguide light L3 is branched by a grating coupler 40 provided in contact with 27, and the light sources 21, 22 are determined based on the amounts of the branched light L4 detected by the light receiving elements 41, 42, 43 formed integrally with the optical module 30. , 23 are adjusted. Therefore, the configuration for adjusting the light amount can be made small and simple, and the adjustment can be performed even during the scanning of the scanning line.

Further, the light source 21 due to a change in the ambient temperature, etc.
Even when the coupling efficiency is reduced due to a change in the relative position between the optical modules 22 and 23 and the optical module 30, the emitted light emitted from the optical module 30 can be kept constant in accordance with the reduction.

Further, since the branch angle of the branch light L4 with respect to the plurality of waveguides 25, 26, and 27 is variable, even if the waveguides 25, 26, and 27 approach, the light receiving elements 41,, and
3 can be arranged at positions where they do not interfere with each other. As a result, the exit surface 25 where the waveguides 25, 26, and 27 approach each other.
b, 26b, 27b, the grating coupler 40
Can be formed, and the detection accuracy of the fluctuation of the emitted light can be improved.

FIGS. 6A and 6B are a plan view and a side view showing a light source device 10 according to a second embodiment. First
The difference from the embodiment is that the light receiving elements 41, 42, 43 are formed before the lower cladding layer 28 is formed, and the guided light L3 (see FIG.
The light is diffracted and branched to the four sides. Other configurations are the same as those of the first embodiment. With such a configuration, the same effect as in the first embodiment can be obtained.

FIGS. 7A and 7B are a plan view and a side view showing a light source device 10 according to a third embodiment. First
The difference from the embodiment is that the light receiving elements 41, 42, 4
One is that one light receiving element 44 is provided instead of 3, and the grating of the grating coupler 40 is formed at a constant period. Other configurations are the same as those of the first embodiment.

According to the present embodiment, each of the waveguides 25, 2
The branched light L4 is radiated from the light receiving elements 44 from 6, 27 in the same direction. When detecting the amount of light emitted from each of the waveguides 25, 26, and 27, the light amount of each branch light can be detected by the light receiving element 44 by separately driving the light sources 21, 22, and 23. And the control unit 31
By adjusting the outputs of the light sources 21, 22, and 23 (see FIG. 3), the light amount of the light beam emitted from the optical module 30 can be kept constant.

In the first to third embodiments described above, the optical module 30 and the light sources 21, 22, and 23 are integrally formed. However, these are formed separately, and the optical fiber and the prism are connected to the optical module. The light beam from the light source may be incident on the light source 30 by being coupled thereto. Further, each of the waveguides 25, 26, 2
The light sources 21, 22, and 23 are provided for every 7, but one light source may be branched so as to be incident on each of the incident surfaces 25a, 26a, and 27a. In this case, an adjusting means for adjusting the light amount of each light beam after branching is separately required.

[0046]

According to the first aspect of the present invention, the guided light is branched by the grating coupler provided in contact with the waveguide, and based on the amount of the branched light detected by the light receiving element formed integrally with the optical module. To adjust the light intensity of the light source. Therefore, the configuration for adjusting the light amount can be made small and simple, and the adjustment can be performed even during the scanning of the scanning line.

Further, even when the coupling efficiency is reduced due to a change in the relative position between the light source and the optical module due to a change in the ambient temperature or the like, the light emitted from the optical module is kept accurately and consistently. can do.

According to the second aspect of the present invention, since the branching direction of the branched light is made variable with respect to the plurality of waveguides, the respective light receiving elements are located at positions where they do not interfere with each other even if the respective waveguides approach. Can be arranged. Accordingly, a grating coupler can be formed in the vicinity of the emission surface where each waveguide approaches, and the detection accuracy of the variation of the emitted light can be improved.

According to the third aspect of the present invention, the gratings of the grating couplers are formed with different periods corresponding to the respective waveguides, so that the branching directions of the respective branched light beams with respect to the respective waveguides can be easily changed. .

According to the fourth aspect of the present invention, since the branching directions of the branched light by the grating coupler are the same, the formation of the grating coupler is easy, and the number of light receiving elements is one and the structure is simplified.

According to the fifth and sixth aspects of the present invention,
The guided light is branched by a grating coupler provided in contact with the waveguide, and the light amount of the light source is adjusted based on the light amount of the branched light detected by the light receiving element formed integrally with the optical module. For this reason, the light source device can be made compact and simple, and the light amount can be adjusted even during scanning of the scanning line.

Further, even when the coupling efficiency is reduced due to a change in the relative position between the light source and the optical module due to a change in the ambient temperature or the like, the light emitted from the optical module can be easily kept constant following the change. can do.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a light beam writing device including a light source device according to a first embodiment of the present invention.

FIG. 2 is a plan view and a side view showing the light source device according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a light source device according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a grating coupler of the light source device according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating the relationship between the height of the grating of the grating coupler and the radiation loss coefficient of the light source device according to the first embodiment of the present invention.

FIG. 6 is a plan view and a side view showing a light source device according to a second embodiment of the present invention.

FIG. 7 is a plan view and a side view showing a light source device according to a third embodiment of the present invention.

FIG. 8 is a plan view and a side view showing a conventional light source device.

FIG. 9 is a perspective view showing a conventional light source.

[Explanation of symbols]

 Reference Signs List 1 light beam writing device 2 collimator lens 3 polygon mirror 4 scanning lens 5 reflection mirror 6 light receiving sensor 10 light source device 11, 16 electrode 12 substrate 13 lower cladding layer 14 active layer 15 upper cladding layer 21, 22, 23 light source 24 substrate 25 , 26, 27 Waveguide 28 Lower cladding layer 29 Upper cladding layer 30 Optical module 31 Control unit 32 Comparison unit 33 Drive unit 34 Storage unit 40 Grating coupler 41, 42, 43, 44 Light receiving element

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01L 31/12 G02B 6/12 B 5F089 H01S 5/0683 H01L 31/02 DF term (reference) 2C362 AA10 AA11 AA14 AA15 AA17 AA53 AA61 AA63 DA08 2H037 AA04 BA02 BA11 CA33 DA03 DA06 2H047 KA03 KA12 MA07 RA08 TA05 TA43 TA47 5F073 AB13 AB21 AB25 AB27 AB29 BA07 FA02 FA06 GA02 GA12 5F088 BA16 BB10 EA09 EA11 JA13 CA16 AC20 FA20 AC20

Claims (6)

[Claims] 1. A waveguide for guiding incident light incident from an incident surface to an exit surface, and a grating formed in contact with the waveguide, the incident light being branched from the waveguide and emitted in a predetermined direction. An optical module, comprising: a grating coupler; and a light receiving element that receives light split by the grating coupler and detects the amount of light. 2. The optical module according to claim 1, wherein a plurality of said waveguides are provided, and said branch light from each of said waveguides is emitted in a different direction. 3. The optical module according to claim 2, wherein the gratings of the grating coupler have different periods corresponding to the respective waveguides. 4. The optical module according to claim 1, wherein a plurality of the waveguides are provided, and the branched light beams from the respective waveguides are emitted in the same direction. 5. An optical module according to claim 1, wherein said light source irradiates a light beam onto said incident surface.
A light source device comprising: a control unit that controls an output of the light source based on a detection result of the light receiving element. 6. The light source device according to claim 5, wherein the optical module and the light source are provided integrally.