KR20110103217A - Light source for tunable wavelength - Google Patents

Abstract

The present invention discloses a tunable light source with improved high speed operation and stability. The light source may include a PLC element disposed on both sides of the lens formed in the housing, and an SLD element. The housing may include a first housing surrounding the SLD element and a second housing surrounding the PLC element. The first housing is connected to the RF connector for transmitting a signal to the SLD device, the second housing may lead the optical fiber connected to the PLC device to the outside.

Description

Light source for tunable wavelength

The present invention relates to a tunable light source, and more particularly to a tunable light source including an external resonant laser device.

The present invention is derived from a study conducted as part of the IT growth engine technology development project of the Ministry of Knowledge Economy [Task Management No .: 2008-S-008-02, Title: FTTH Advanced Optical Component Technology Development].

In order to implement an economical WDM subscriber network system, it is necessary to develop a stable and cost effective light source. In view of this, three types of light sources for WDM-PON have been developed. First, when FP-LD is used as the light source of WDM subscriber network with Wavelength-locked (WL) FP-LD, transmission characteristics are degraded due to mode division noise. It is known that Gb / s data transmission is possible. Secondly, the RSOA for the loop-back type WDM-PON that directly modulates the downlink optical signal by using the RSOA of the re-modulation scheme is being actively studied, and data transmission is possible up to 2.5 Gb / s. It is known. Third, the method uses PLC-ECL, a wavelength variable light source.

On the other hand, the ultra-high speed light source (for 2.5 ~ 10Gbps) using an external resonant laser device (ECL) includes a fiber bragg grating (FBG) structure and a grating fabricated on a silica waveguide. The ECL described above has a disadvantage in that FBG and silica-based devices are difficult to apply in ECL fabrication having wavelength tunable characteristics because they have characteristics that are difficult to tunable.

The problem to be solved by the present invention is to provide a variable wavelength light source capable of variable wavelength of 25nm or more, operating at a high speed of 2.5Gbps to 10Gbps class.

In addition, another object of the present invention is to provide a variable wavelength light source that can improve the coupling performance and stability of the optical element.

In order to achieve the above object, the present invention provides a variable wavelength light source. Its light source includes a housing; A lens formed inside the housing; A flat plate optical circuit element formed in the housing on one side of the lens; And a super luminescent diode element formed in the housing on the other side of the lens opposite to the planar optical circuit element.

As described above, according to the problem solving means of the present invention, there is an effect that can improve the coupling performance and stability by arranging the plate type optical circuit element and the external resonant laser device in the housing.

In addition, by connecting the RF connector for applying an electrical signal to the external resonance laser device to the housing there is an effect that can be operated at a high speed of 2.5Gbps to 10Gbps class.

1 is a plan view schematically showing a variable wavelength light source according to a first embodiment of the present invention.
2 and 3 are cross-sectional views taken along line II ′ of FIG. 1.
4 is a perspective view illustrating the SLD element of FIGS. 1 to 3.
FIG. 5 is a cross-sectional view illustrating a buried-ridge waveguide (B-RWG) optical waveguide of FIG. 4. FIG.
6 and 7 are cross-sectional views taken along line II-II 'of FIG. 1;
8 is a perspective view illustrating the PLC device of FIG. 1.
9 is a plan view illustrating that the SLD device and the PLC device of FIG. 1 are inclined.
10 is a plan view schematically showing a variable wavelength light source according to another embodiment of the present invention.
FIG. 11 is a plan view showing that the laser device and the PLC device of FIG. 10 are disposed to be inclined. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and methods of achieving the same will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in different forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the invention to those skilled in the art, and the invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms 'comprises' and / or 'comprising' mean that the stated element, step, operation and / or element does not imply the presence of one or more other elements, steps, operations and / Or additions. In addition, since they are in accordance with the preferred embodiment, the reference numerals presented in the order of description are not necessarily limited to the order. In addition, in the present specification, when it is mentioned that a film is on another film or substrate, it means that it may be formed directly on the other film or substrate or a third film may be interposed therebetween.

In addition, the embodiments described herein will be described with reference to cross-sectional and / or plan views, which are ideal exemplary views of the present invention. In the drawings, the thicknesses of films and regions are exaggerated for effective explanation of technical content. Accordingly, shapes of the exemplary views may be modified by manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention are not limited to the specific forms shown, but also include variations in forms generated by the manufacturing process. For example, the etched regions shown at right angles may be rounded or have a predetermined curvature. Accordingly, the regions illustrated in the figures have schematic attributes, and the shape of the regions illustrated in the figures is intended to illustrate a particular form of region of the device and not to limit the scope of the invention.

1 is a plan view schematically showing a variable wavelength light source according to a first embodiment of the present invention.

Referring to FIG. 1, the wavelength variable light source according to the first embodiment of the present invention may include a planar lightwave circuit (PLC) element formed on one side of the lens 6 in the housings 11 and 21. 13) and a super luminescent diode (SLD) element 9 formed on the other side of the lens 6. Here, the housings 11 and 21 may include a first housing 11 surrounding the SLD element 9 and a second housing 21 surrounding the PLC element 13. Accordingly, the variable wavelength light source according to the first embodiment of the present invention includes a PLC element 13 packaged on one side in the housings 11 and 21 and an SLD element 9 packaged on the other side in the housings 11 and 21. Since it can improve the coupling performance and stability of the optical elements.

The lens 6 may be disposed at the end of the first housing 11 to increase the coupling efficiency of the SLD element 9 and the PLC element 13. For example, the lens 6 may comprise an aspherical convex lens. Reference numeral “7” is a monitoring light detector.

The first housing 11 may be connected to the RF connector 1 for operating the SLD element 9 at high speed. The RF connector 1 can cause the SLD element 9 to operate at a high speed of 2.5 Gbps to 10 Gbps. The RF connector 1 may be electrically connected to the SLD element 9 through the RF lead frame 2 and the impedance matching resistor 3. The first housing 11 may be coupled to the housing cover 10 formed at the end of the RF connector 1. The first housing 11 may be formed of a metal material such as SUS. For example, the first housing 11 and the SLD element 9 may be arranged as shown in FIGS. 2 and 3.

2 and 3 are cross-sectional views taken along line II ′ of FIG. 1, and the first housing 11 may have a rectangular or circular internal space cross section for receiving the SLD element 9. Inside the first housing 11, a first thermoelectric cooler 5 and a submount 8 may be bonded in a stack to stabilize the temperature of the SLD element 9. The SLD element 9 and the first thermistor 4 may be bonded onto the submount 8. The first thermoelectric cooler 5 may be supported flat as in FIG. 3 by the block 23 at the bottom of the first housing 11 having a circular inner space. Therefore, the first housing 11 can accommodate the SLD element 9 flatly in the rectangular or circular internal space.

The SLD element 9 may include an external cavity laser device to which a Ridge-Semiconductor Optical Amplifier (hereinafter referred to as R-SOA) is connected.

4 is a perspective view illustrating the SLD device of FIGS. 1 to 3, and FIG. 5 is a cross-sectional view illustrating a buried-ridge waveguide (B-RWG) optical waveguide of FIG. 4.

4 and 5, in the SLD device 9, an n-InP buffer layer 62 is grown on the semi-insulating InP substrate 61 by about 0.5 to 1 μm, and the InGaAsP passive waveguide layer 63 is n. InP lower cladding layer 64, active layer 65 and upper cladding layer 69 may be stacked in this order. Here, the teijin waveguide region 66 may be integrated into the active layer 65 by a butt-coupling method. The SLD element 9 has a straight waveguide region, a curved waveguide region, and a tapered waveguide region 66, and the entire region may be formed of a BH structure. The semi-insulating InP substrate 61 may reduce the parasitic capacitance of the SLD element 9. The current blocking layers 68, 67, and 64 can block current flow out of the active layer 65. The current blocking layers 68, 67, and 64 and the trench 76 can reduce parasitic capacitance leaking around the active layer 65. Channel 76 includes a trench and may be formed by selective etching of a portion of substrate 61. The buried ridge waveguide (B-RWG) waveguide 73 may increase coupling efficiency of the tapered waveguide region 66 with a silica waveguide, an optical fiber, or the like.

Ridge waveguides can be formed to about 11 μm by simple photo and selective etching. In the exemplary embodiment of the present invention, the width of the InGaAsP passive waveguide layer 63 formed under the ridge waveguide in order to narrow the radiation angle to a circular or 15 degrees or less may be 3 to 9 μm to form the B-RWG waveguide 73.

The SLD element 9 may include an antireflection coating 74 formed at the end of the B-RWG waveguide and a high reflection coating 75 formed at the end of the straight waveguide region opposite thereto. The antireflective coating 74 may lower the reflectivity of the exit cross section. The high reflection coating 75 can increase the gain of the optical device. The active layer 65 has a stress relaxation multi-quantum well structure in the case of SLD and SOA, and a stress relaxation bulk structure in the case of R-SOA and SOA.

The coupling efficiency of the waveguide light under the active layer 65 can be improved. In addition, the passive waveguide region 63 can reduce the absorption loss of light in the InP layer outside the tapered waveguide region 66. Tilting the optical waveguide at a larger angle lowers the reflectance at the entrance and exit surfaces and reduces the gain because of the large losses in the curved waveguide region. In this case, the passive waveguide region 63 may increase coupling efficiency to minimize generation of light loss. For example, the width of the active layer 65 may be 1 to 1.5 μm, and the width may be reduced from 1 to 1.5 μm to 0.1 μm or less from the curved waveguide to the end of the tapered waveguide region 66.

Meanwhile, the second housing 21 may be formed to surround the PLC element 13 while communicating with the first housing 11. The second housing 21 may lead the optical fiber 19 connected to the PLC element 13 to the outside.

6 and 7 are cross-sectional views taken along line II-II ′ of FIG. 1, and FIG. 8 is a perspective view illustrating the PLC device of FIG. 1.

6 to 8, the second housing 21 and 21 may lead the optical fiber 19 and the lead frame 22 connected to the polymer PLC element 13 to the outside. The polymer PLC element 13 is bonded on the second thermoelectric cooler 17 and may be formed on the silica or silicon PLC platform 30, the lower polymer cladding layer 31, and the upper polymer cladding layer 32. The polymer PLC device 13 may include a polymer waveguide 14, a polymer grating 16, and an electrode 15. When a current is applied to the electrode 15, heat is generated, and the refractive index of the polymer grating 16 is changed to change the wavelength. In addition, a second thermistor 18 may be bonded to the second thermoelectric cooler 17 next to the polymer PLC element 13 and each part of the PLC element 13 may be connected to the lead frame 22 and the bonding wire 20. Can be connected by The optical fiber 19 is bonded to the output terminal of the PLC element 13. The input interface of the PLC element 13 may be inclined by about 5 to 15 degrees in order to reduce reflectivity.

FIG. 9 is a plan view illustrating an inclination of the SLD device and the PLC device of FIG. 1, and when the PLC device 13 is inclined with the laser device about 3 ° to about 7 °, coupling efficiency may be increased.

10 is a plan view schematically illustrating a tunable light source according to another embodiment of the present invention. Referring to FIG. 10, in the wavelength variable light source according to another exemplary embodiment, the RF connector 1 may be connected to the first housing 11 in a direction perpendicular to the second housing 21.

FIG. 11 is a plan view illustrating an inclination of the SLD device and the PLC device of FIG. 10. When the PLC device 13 is inclined with the laser device about 3 ° to about 7 °, coupling efficiency may be increased.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood. It is therefore to be understood that the above-described embodiments are illustrative and non-restrictive in every respect.

1: RF Connector 2: RF Lead Frame
3: impedance matching resistor 4: first thermistor
5: first thermoelectric cooler 6: lens
7: monitoring light detector 8: submount
9: SLD element 10: Housing cover
11: first housing 12: first lead frame
13: PLC element 14: polymer waveguide
15 electrode 16 polymer grating
17: second thermoelectric cooler 18: second thermistor
19: optical fiber 20: wire bonding
21: second housing 22: second lead frame
23: block 30: PLC platform
31: polymer cladding layer below 32: polymer cladding layer below
61 Si-InP substrate 62 n-InP buffer layer
63: Passive Waveguide 64: n-InP Clad Layer
65 active layer 66 tapered waveguide
67: p-InP current blocking layer 68: n-InP current blocking layer
69: P-InP clad layer 70: p-InGaAs ohmic layer
71: p-type electrode 72: n-type electrode
73: Buried ridge waveguide area 74: Antireflective coating surface
75: high reflection coating surface 76: channel

Claims (1)

housing;
A lens formed inside the housing;
A flat plate optical circuit element formed in the housing on one side of the lens; And
And a super luminescent diode element formed in the housing on the other side of the lens opposite the planar optical circuit element.

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