TWI646742B - Laser chip and laser diode for mobile fronthaul - Google Patents

Abstract

A laser chip and a laser diode which can be applied to a mobile front end, and a ridge-type waveguide structure, which is divided into an amplification area and a work area, the reflectance of the end face of the amplification area is reduced to less than 0.1%, and the reflectance of the end face of the work area is improved. To over 99%. The incident light is injected into the amplification region to increase the optical power to facilitate mode locking in the work area. After the working area is clamped, the same wavelength as the incident light is generated, and a modulation signal is added to the working area to achieve the purpose of transmitting the signal.

Description

Laser chip and laser diode for mobile front end

The present invention relates to a process technology, and more particularly to a laser chip and a laser diode that can be applied to a Mobile Fronthaul (MFH).

With the evolution of information and communication technology, smart phones or other mobile devices have been launched in large numbers, and the demand for mobile Internet access is increasing day by day. In order to maintain the mobile Internet speed and service quality, it is necessary to build a dense base station to meet the daily growth. Mobile broadband demand. In the establishment of the mobile network, the baseband unit (BBU) in the base station is separated from the radio remote unit (RRU), and the BBU is deployed centrally to meet low cost, high capacity, and low power consumption. The BBU and the RRU are connected by using a fiber-optic network. Currently, the BBU and the RRU are connected by using Coarse Wavelength Division Multiplexing (CWDM) technology to effectively use the optical fiber, as shown in FIG. 1 .

Generally, the CWDM multiplexer/demultiplexer 101 and 102 channels are adjacent to each other at 20 nm (nm), and each channel uses optical modules of different wavelengths to increase the operation and preparation cost. If Point to Point Wavelength Division Multiplexing (PtP WDM) is used, as shown in FIG. 2, the BBU 206 uses an L-band laser diode, and the RRU 207 uses a C-band Ray. The emitter diode, the multiplexer/demultiplexer 201, 202 has periodicity, and the C-Band Amplified Spontaneous Emission (ASE) 204 is cut by the optical fiber 203, the multiplexer/demultiplexer 201, and injected into the RRU. In the laser diode of 207, after the mode-locking, the same wavelength as that of the injected light is generated. The L-Band ASE 205 is diced by the multiplexer/demultiplexer 202 and injected into the laser diode of the BBU 206, and is clamped to produce the same wavelength as the injected light. After being cut by the multiplex through the multiplexer/demultiplexer, it is injected into the laser diode, and after the mode-locking, the same wavelength as the injected light is generated, and the colorless light source is achieved.

However, it is known that a laser diode for injection molding has a good clamping effect, and a Buried structure is required, which requires secondary epitaxy, which increases component cost and complexity and reduces yield.

In view of this, the inventor of the present invention has improved and innovated, and proposed a laser chip and a diode design, which is fabricated by using a ridge waveguide structure laser wafer without secondary epitaxy to reduce components. Cost, increase yield, increase the amplification area in the laser wafer to reduce the injected light power.

The object of the present invention is to provide a laser diode, which uses a ridge waveguide structure and has an amplification power function, and reduces the intensity of the injected light to achieve a colorless light source in the use of the injection mold.

A laser wafer design capable of achieving the above object of the invention is to fabricate a ridge waveguide structure on a commercially available laser diode epitaxial structure. The laser wafer of the present invention applicable to MFH includes a substrate and an N-type embossed wafer. Coating, active layer, P-type cladding layer, first ohmic contact layer, second ohmic contact layer, patterned insulating layer, first P-type contact metal layer, second P-type contact metal layer, N-type contact a metal layer, a low reflection layer, and a highly reflective layer. The N-type cladding layer is disposed on one side of the substrate. The active layer is disposed on the N-type cladding layer. The P-type cladding layer is disposed on the active layer, and the P-type cladding layer is in the shape of a ridge mesa, which is used as an optical waveguide to spread the signal light along the optical path extending in the direction of the P-type cladding layer. . The first ohmic contact layer is disposed on the P-type cladding layer. The second ohmic contact layer is disposed on the P-type cladding layer and after the first ohmic contact layer. The patterned insulating layer covers the first ohmic contact layer, the second ohmic contact layer, and the P-type cladding layer, and exposes a portion of the first ohmic contact layer and the second ohmic contact layer. The first P-type contact metal layer is disposed on a region of the first ohmic contact layer that is not covered by the patterned insulating layer. The second P-type contact metal layer is disposed on a region of the second ohmic contact layer that is not covered by the patterned insulating layer. The N-type contact metal layer is disposed on the other side of the substrate. The low reflection layer is disposed on one side of the P-type cladding layer perpendicular to the light path. The highly reflective layer is disposed on one side of the P-type cladding layer perpendicular to the light path.

The laser diode of the present invention applicable to MFH includes a germanium wafer, an optical fiber, a first waveguide region, a modulator wafer, a second waveguide region, a FP laser wafer, and a third waveguide region. The optical fiber is fixed to one end of the germanium wafer by glass, and one end of the optical fiber receives an external optical signal. One end of the first waveguide region is connected to the other end of the optical fiber relative to the received optical signal. The modulator wafer is disposed at the other end of the first waveguide region relative to the optical fiber. The second waveguide region is disposed at the other end of the modulator wafer relative to the first waveguide region. The FP laser wafer is disposed at the other end of the second waveguide region opposite the modulator wafer. The third waveguide region is disposed at the other end of the FP laser wafer relative to the second waveguide region.

The laser diode of the present invention, which can be used for MFH, includes a germanium wafer, an optical fiber, a first spherical lens, a modulator wafer, a second spherical lens, and an FP laser wafer. The optical fiber is fixed to one end of the germanium wafer by a glass, and one end of the optical fiber receives an external optical signal. The first spherical lens is disposed at the other end of the optical fiber receiving optical signal. The modulator wafer is disposed at the other end of the first spherical lens relative to the optical fiber. The second spherical lens is disposed at the other end of the modulator wafer relative to the first spherical lens. The FP laser chip is disposed at the other end of the second spherical lens relative to the modulator wafer.

Thereby, the laser chip and the laser diode can be divided into two regions, one being an enlarged area and the other being a working area. The magnified area increases the power of the injected light and increases the clamping effect. The working area provides operating bias and upload modulation signals. After being cut by the multiplexer/demultiplexer, the ASE is injected into the amplification area to be amplified, and then transmitted to the work area by the ridge waveguide to operate at the desired working point and upload the modulation signal.

The above described features and advantages of the invention will be apparent from the following description.

The specific embodiments are described below to illustrate the embodiments of the invention, but are not intended to limit the scope of the invention.

First embodiment

The full structure of the laser diode epitaxial wafer 300 is as shown in FIG. 3, and the upper surface of the indium phosphide (InP) substrate 301 is epitaxially grown from bottom to top, and N-type cladding is composed of N-type indium phosphide (InP). N type cladding layer 302, an active layer 303 composed of a quantum well of phosphorus indium gallium arsenide (InGaAsP), and a P-type cladding layer composed of P-type indium phosphide (P type cladding) A layer 304 and an ohmic contact layer 305 composed of indium arsenide (InGaAs).

In the structure of Fig. 3, a ridge-shaped waveguide structure in the form of a ridge mesa is formed, which is used as an optical waveguide, so that the signal light can be confined to the ridge-like region and is diced along the P-type. The light path of the ridge waveguide extending direction formed by the cladding layer 304 propagates. The fabrication steps are as follows: a strip-shaped waveguide is defined along the direction of the epitaxial wafer of FIG. 3 using optical lithography, and then the P-type cladding layer 304 and the ohmic contact layer 305 are etched using chemical etching, that is, the ridge waveguide structure is completed. . The front view of the ridge waveguide can be seen in Fig. 4, which is a view taken at a 90 degree angle with respect to Fig. 3.

Next, a patterned insulating layer 406 is formed on the epitaxial wafer 300 completing the ridge waveguide structure for insulation. Through this step, the epitaxial wafer 300 will expose the top semiconductor, and the user can pass through the exposed region. Input Current. The step of patterning the insulating layer 406 is as follows: using a Plasma Enhanced Chemical Vapor Deposition (PECVD), a tantalum nitride (SiNx) is grown on the entire epitaxial wafer 300 of the completed ridge waveguide, and then a photoresist is deposited on the tantalum nitride, and the photoresist is etched using an Oxygen plasma until the tantalum nitride at the top of the ridge waveguide is exposed, and then etched with a carbon fluoride ion (CF4 plasma) to expose the ridge. The tantalum nitride on top of the waveguide is removed until the semiconductor layer is exposed, and then the photoresist is removed, that is, the patterned insulating layer 406 is completed.

Next, an electrode of the component is defined on the epitaxial wafer 300 for current input. First, a photoresist having image reversal characteristics is used, and an optical lithography technique is used to define an electrode separation pattern on a region of the ridge waveguide, and then exposed to ultraviolet light and developed to expose the ohmic contact layer 305. Then, a P-type contact metal layer 407 is grown on the ohmic contact layer 305 by using a vacuum electron beam evaporation system. After the evaporation is completed, the epitaxial wafer 300 is bubbled in acetone to remove the unnecessary metal, thereby forming the first P-type. The metal layer 507 and the second P-type contact metal layer 508 are contacted. The ohmic contact layer 305 is chemically etched to form a first ohmic contact layer 505 and a second ohmic contact layer 506 are respectively disposed on the P-type cladding layer 304, as shown in FIG. The first ohmic contact layer 505 is at the amplification region and the second ohmic contact layer 506 is at the work region.

Wherein, the foregoing patterned insulating layer 406 will cover the first ohmic contact layer 505, the second ohmic contact layer 506, the P-type cladding layer 304, the first P-type contact metal layer 507 and the second P-type contact metal. Layer 508 and a portion of the first ohmic contact layer 505 and the second ohmic contact layer 506 are exposed. The first P-type contact metal layer 507 is disposed on the first ohmic contact layer 505 and is not covered by the patterned insulating layer 406. The second P-type contact metal layer 508 is disposed on the second ohmic contact layer 506. The area covered by the patterned insulating layer 406.

Next, the indium phosphide (InP) substrate which has completed the above steps is thinned, and is on the other side of the indium phosphide substrate 301 of the epitaxial wafer 300, that is, the indium phosphide substrate 301 is opposite to the other side of the elongated ridge waveguide. The N-type contact metal layer 408 is vapor-deposited, and an Fabry-Perot (FP) laser wafer is obtained by annealing and cutting. Then, on both sides of the epitaxial wafer 300, that is, on both sides of the epitaxial wafer 300 perpendicular to the optical path of the signal light (the ridge waveguide extending direction), the low-reflection layer 509 is vapor-deposited using a vacuum electron beam evaporation system. The reflective layer 510, as shown in FIG. 5, wherein the low and high reflective layers 509, 510 are at least covered by the P-type cladding layer 304, that is, disposed on one side of the P-type cladding layer 304 perpendicular to the optical path. The low reflection layer 509 is for reducing the reflectance of the injected light, and increasing the ratio of the injected signal light. The high reflection layer 510 allows the light to be output by the low reflection layer. The reflectance of the low reflection layer 509 is less than 0.1%, and the reflectance of the high reflection layer 510 is greater than 99%.

Finally, the indium phosphide substrate 301, the N-type cladding layer 302, the active layer 303, the P-type cladding layer 304, the first ohmic contact layer 505, the second ohmic contact layer 506, the patterned insulating layer 407, A P-type contact metal layer 507, a second P-type contact metal layer 508, an N-type contact metal layer 408, and a low-reflection layer 509 are combined with the high-reflection layer 510 to form the FP laser wafer 500.

Second embodiment

In order to increase the transmission rate in the injection mode-locking mechanism, the present invention further proposes a second embodiment of a laser diode applicable to the MFH, see FIG. In this embodiment, a first waveguide region 604, a second waveguide region 606, and a third waveguide region 608 are formed on the germanium wafer 609 using a Planar Lightwave Circuit technique, using micro-developing techniques and chemical etching or using An electron cyclotron resonance reactive ion etching (ECR-RIE) method etches an optical waveguide and a semiconductor to form a metal conductive layer region, and forms a first metal conductive layer 610 using a micro-developing technique and a thin film technique. The second metal conductive layer 611 and the conductive varnish 607 and the FP laser 607 are respectively adhered to the first metal conductive layer 610 and the second metal conductive layer 611, and the FP laser wafer 607 is The FP laser wafer that is ultimately formed by the structure of an embodiment or FP laser wafer that is typically used for injection molding.

The optical fiber 601 is fixed on one end of the silicon wafer 609 by the glass 602. One end of the optical fiber 601 receives an external optical signal (not shown), and one end of the first waveguide region 604 is connected to the optical fiber 601 to receive the other end of the optical signal. The transformer chip 605 is disposed at the other end of the first waveguide region 604 opposite to the optical fiber 601, and the second waveguide region 606 is disposed at the other end of the modulator wafer 605 with respect to the first waveguide region 604, and the FP laser wafer 607 is disposed at The second waveguide region 606 is opposite the other end of the modulator wafer 605, and the third waveguide region 608 is disposed at the other end of the FP laser wafer 607 opposite the second waveguide region 606.

The optical fiber 601 introduces an optical signal into the first waveguide region 604, and is guided by the first waveguide region 604 through the modulator wafer 605 and the second waveguide region 606, and then injected into the FP laser wafer 607, and locked by the FP laser wafer 607. The light is then output and directed through the second waveguide region 606 to the modulator wafer 605, at which time the modulator wafer 605 is modulated with a modulated signal and directed by the first waveguide region 604 to the fiber output. The modulator wafer 605 can be an electronic absorption modulator, a Mach Zender modulator.

Finally, the laser diode 600 is formed by the combination of the germanium wafer 609, the optical fiber 601, the first waveguide region 604, the modulator wafer 605, the second waveguide region 606, the FP laser wafer 607, and the third waveguide region 608.

Third embodiment

In order to increase the transmission rate in the injection mode-locking mechanism, the present invention further proposes a third embodiment of a laser diode applicable to the MFH, see FIG. In this embodiment, the semiconductor is etched using a micro-developing technique and a chemical etching or an electron cyclotron resonance reactive ion etching (ECR-RIE) method to form a V-shaped trench, and an adhesive is used separately. The first spherical lens 704 and the second spherical lens 706 are adhered to the V-shaped groove. The first metal conductive layer 709 and the second metal conductive layer 710 are formed by using a micro-developing technique and a thin film technique, and the modulator wafer 705 and the FP laser wafer 707 are respectively adhered to the first metal conductive layer 709 and the second using a conductive adhesive. The metal conductive layer 710, and the FP laser wafer 707 is the structure of the first embodiment, ultimately forming a FP laser wafer or a FP laser wafer typically used for injection molding.

The optical fiber 701 is fixed to one end of the germanium wafer 708 by the glass 702. One end of the optical fiber 701 receives an external optical signal, and the first spherical lens 704 is disposed at the other end of the optical fiber 701 for receiving the optical signal, and the modulator chip 705 is The first spherical lens 704 is disposed at the other end of the optical fiber 701, the second spherical lens 706 is disposed at the other end of the modulator wafer 705 with respect to the first spherical lens 704, and the FP laser wafer 707 is disposed at the second end. The spherical lens 706 is opposite the other end of the modulator wafer 705.

The optical fiber 701 introduces the optical signal into the first spherical lens 704 to focus and inject into the modulator wafer 705, and then is focused and injected into the FP laser wafer 707 by the second spherical lens 706, and is clamped by the FP laser wafer 707 before being output. The light is focused and injected into the modulator wafer 705 via the second spherical lens 706. At this time, the modulator wafer 705 is added with a modulation signal, and then focused by the first spherical lens 704 to the output of the optical fiber 701. The modulator wafer 705 can be an electronic absorption modulator, a Mach Rende modulator.

Finally, the laser diode 700 is formed by the combination of the germanium wafer 708, the optical fiber 701, the first spherical lens 704, the modulator wafer 705, the second spherical lens 706, and the FP laser wafer 707.

Features and effects

The embodiment of the invention provides a laser wafer and a laser diode applicable to the MFH, and has the following advantages: (1) using the injection mode-locking to achieve a colorless light source, reducing the operation and preparation cost, and increasing the number of channels. (2) It is made of ridge-shaped waveguide structure, which does not require secondary epitaxy, increases yield and reduces production cost. (3) Increase the amplification area to reduce the injected light power. (4) Increase the transmission rate.

The detailed description of the present invention is intended to be illustrative of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. In the scope of patents.

To sum up, this case is not only innovative in terms of technical thinking, but also has many of the above-mentioned functions that are not in the traditional methods of the past. It has fully complied with the statutory invention patent requirements of novelty and progressiveness, and has applied for it according to law.

101‧‧‧Multiplex/Demultiplexer

102‧‧‧Multiplex/Demultiplexer

103‧‧‧Fiber

104‧‧‧BBU

105‧‧‧RRU

201‧‧‧Multiplex/Demultiplexer

202‧‧‧Multiplex/demultiplexer

203‧‧‧Fiber

204‧‧‧C-Band ASE

205‧‧‧L-Band ASE

206‧‧‧BBU

207‧‧‧RRU

301‧‧‧Substrate

302‧‧‧N type coating

303‧‧‧ active layer

304‧‧‧P type coating

305‧‧‧ Ohmic contact layer

406‧‧‧ nitride

407‧‧‧P type contact metal layer

408‧‧‧N type contact metal layer

500‧‧‧Laser Wafer

505‧‧‧First ohmic contact layer

506‧‧‧second ohmic contact layer

507‧‧‧First P-type contact metal layer

508‧‧‧Second P-type contact metal layer

509‧‧‧Low reflective layer

510‧‧‧High reflection layer

600‧‧‧Laser diode

601‧‧‧ fiber

602‧‧‧ glass

603‧‧‧ fiber optic

604‧‧‧First waveguide area

605‧‧‧Transformer chip

606‧‧‧Second waveguide area

607‧‧‧FP laser wafer

608‧‧‧ Third waveguide area

609‧‧‧矽 wafer

610‧‧‧First metal conductive layer

611‧‧‧Second metal conductive layer

700‧‧‧Laser diode

701‧‧‧ fiber

702‧‧‧ glass

703‧‧‧Fiber

704‧‧‧First spherical lens

705‧‧‧Transformer chip

706‧‧‧Second spherical lens

707‧‧‧FP laser wafer

708‧‧‧矽 wafer

709‧‧‧First metal conductive layer

710‧‧‧Second metal conductive layer

Figure 1 is a conventional MFH network diagram. 2 is a conventional PtP WDM network diagram of injection mode locking. 3 is a structural view of a laser wafer applied to an MFH according to a first embodiment of the present invention. 4 is a first process flow diagram of a laser wafer applied to an MFH in accordance with a first embodiment of the present invention. Figure 5 is a flow chart showing the second fabrication of a laser wafer applied to the MFH in accordance with the first embodiment of the present invention. Figure 6 is a structural view of a laser diode applied to an MFH according to a second embodiment of the present invention. Fig. 7 is a view showing the configuration of a laser diode applied to an MFH according to a third embodiment of the present invention.

Claims (9)

A Fabry-Perot (FP) laser wafer applicable to a Mobile Fronthaul (MFH), comprising: a substrate; an N-type cladding layer disposed on one side of the substrate An active layer disposed on the N-type cladding layer; a P-type cladding layer disposed on the active layer, the P-type cladding layer having a ridge mesa shape, For use as an optical waveguide, the signal light propagates along the optical path of the P-type cladding layer; a first ohmic contact layer is disposed on the P-type cladding layer; and a second ohmic contact current a layer disposed on the P-type cladding layer and adjacent to the first ohmic contact layer according to a spacing; a patterned insulating layer covering the first ohmic contact layer, the second An ohmic contact layer, and the P-type cladding layer, and exposing a portion of the first ohmic contact layer and the second ohmic contact layer; a first P-type contact metal layer disposed on the first ohmic layer a region of the contact layer that is not covered by the patterned insulating layer; a second P-type contact metal layer disposed on the second a region of the contact layer that is not covered by the patterned insulating layer; an N-type contact metal layer disposed on the other side of the substrate; and a low-reflection layer disposed on the P-type film perpendicular to the light path One side of the cladding; a highly reflective layer disposed on one side of the P-type cladding layer perpendicular to the optical path, wherein the first ohmic contact layer is an amplification region, and the second ohmic contact layer is a working region. The FP laser wafer applicable to MFH according to claim 1, wherein the low reflection layer has a reflectance of less than 0.1%. The FP laser wafer applicable to MFH according to claim 1, wherein the high reflection layer has a reflectance greater than 99%. A laser diode applicable to an MFH, comprising: a germanium wafer; an optical fiber fixed to one end of the germanium wafer by a glass, one end of the optical fiber receiving an external optical signal; and a first waveguide region, the first waveguide region One end of the first waveguide region is connected to the other end of the optical fiber opposite to the received optical signal; a modulator wafer is disposed on the other end of the first waveguide region opposite to the optical fiber; and a second waveguide region is disposed on the modulator chip The other end of the first waveguide region; the FP laser wafer according to claim 1 is disposed at the other end of the second waveguide region opposite to the modulator wafer; and a third waveguide region is disposed The FP laser wafer is opposite the other end of the second waveguide region. A laser diode applicable to MFH as described in claim 4, wherein the modulator wafer is an electronic absorption modulator. A laser diode applicable to an MFH as described in claim 4, wherein the modulator wafer is a Mach Rende modulator. A laser diode applicable to an MFH, comprising: a germanium wafer; an optical fiber fixed to one end of the germanium wafer by a glass, one end of the optical fiber receiving an external optical signal; and a first spherical lens The first spherical lens is disposed at the other end of the optical fiber receiving optical signal; a modulator chip is disposed at the other end of the first spherical lens relative to the optical fiber; and a second spherical lens is disposed The FP laser wafer of the first spherical lens is opposite to the first spherical lens; and the FP laser wafer according to claim 1 is disposed on the second spherical lens opposite to the modulator wafer. One end. A laser diode applicable to an MFH as described in claim 7 wherein the modulator wafer is an electronic absorption modulator. The laser diode applicable to the MFH according to claim 7, wherein the modulator chip is a Mach Rende modulator.