Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
  • H01S5/11—Comprising a photonic bandgap structure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
  • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
  • H01S5/1203—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers over only a part of the length of the active region
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
  • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
  • H01S5/125—Distributed Bragg reflector [DBR] lasers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
  • H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure

Definitions

• Laser devices are commonly used as light sources, and it is of particular interest to be able to obtain laser sources which have high quality spectral performance for data communication applications. It is of particular interest to be able to manufacture such devices in a relatively simple and low cost way, to achieve a robust device. In particular it is advantageous to achieve a device with a highly selective optical spectrum, that -is, a device which produces a large amplitude peak at one specific wavelength of output light.
• DBR Distributed Bragg Reflector
• the present invention relates to a laser device, with a ridge waveguide, with a distributed reflector on either side of the central ridge.
• the reflector can be obtained by etching into the active layer on either side of the waveguide . This has the advantage that the reflector can be obtained without using additional regrowth steps.
• the reflector takes the form of a two- dimensional pattern. This allows efficient reflection, while allowing the reflector to be contained in a relatively short length of the device.
• Figure 1 is a plan view of a laser device in accordance with the invention.
• Figure 2 is an enlarged schematic illustration of a region of Figure 1.
• Figure 3 is a cross-sectional view through the device of Figure 1.
• Figure 4 illustrates the room temperature (20°C) CW optical spectra at 60mA for (a) pre-etch non-AR coated and (b) post-etch AR coated conditions of the device of Figure 1.
• Figure 5 illustrates the post-etch room temperature (20°C) CW L-I characteristics of the device of Figure 1.
• Figure 6 illustrates the post-etch, room temperature (20°C) variation of lasing wavelength with CW bias current for the device of Figure 1.
• FIG. 1 is a top plan view of a laser device in accordance with the invention.
• the device 2 is an InGaAsP-InP laser, with a ridge-waveguide 4.
• the device consists of seven 0.8% compressively strained quantum wells, and operates at a centre wavelength of ⁇ 1.29 ⁇ m.
• the laser is 350 ⁇ m long, and acts as a Fabry- Perot (F-P) laser. It is cleaved on both end facets 6,8.
• the laser is bonded junction side up on a temperature-controlled submount (not shown) and the output can be connected via a lensed fibre.
• the back facet 6 is AR coated to 0.1%, in order to suppress the F-P modes.
• Figure 3 is a cross-sectional view, taken on line A-A in Figure 1.
• the device has an active region 10 within the structure, with a silicon dioxide layer 12, having a metal layer 14 above it as the uppermost layers.
• the central ridge- waveguide has a width W of, for example, approximately 3 ⁇ m, with etched channels of width X of approximately 8 ⁇ m on either side of the ridge waveguide.
• a distributed reflector structure is provided on either side of the central ridge waveguide, leaving the waveguide itself untouched.
• the distributed reflectors take the form of an etched 2D-lattice grating 18.
• the grating 18 is etched into the bottom surfaces 20 of the channels 16, over a section of the cavity. This section has a length L of approximately 50 ⁇ m, and is located towards the back facet 6 of the device, for example approximately 50 ⁇ m from the back facet .
• Figure 2 is an enlarged view of the etched grating pattern in one of the channels 16.
• the array comprises a series of holes 22, etched through the top contact 14 to a depth which is comparable to the depth of the active region 10.
• the holes 22 are arranged in a hexagonal array. That is, each hole away from the edge of the array is surrounded by six equally spaced holes. This separation a is of the order of 0.60-0.65 ⁇ m, and the holes have a radius r such that the radius-to-pitch ratio r:a is 0.17, although it may be in the range of 0.17-0.33.
• the grating pattern could also be a square array, or any pattern which provides a suitable reflector.
• the holes are etched to a depth which is very close to, or, more preferably, into the active region.
• the holes can be obtained by postprocessing using any available etching technique, for example, focused ion bean etching (FIBE)or reactive ion etching (RIE) , without requiring any subsequent regrowth.
• FIBE focused ion bean etching
• RIE reactive ion etching
• This structure has the further advantage that the holes, which act as the reflectors, provide a high refractive index contrast ratio between the holes and the material of the device, of approximately 1:3.5.
• the post-etch performance of the device is characterised in terms of the optical spectra. Measurements are taken at room temperature (20°C) under CW bias conditions. Figure 4a shows the pre-etch spectrum before AR coating at 60mA. This is indicative of a typical multi longitudinal mode F-P structure.
• Figure 4b illustrates clearly that, after etching, the device lases in a single longitudinal mode. Purely single mode operation is maintained over the entire operating current range up to over 3 times threshold. A typical SMSR value of >30dB is measured.
• Figure 6 which shows the variation of peak wavelength with CW bias current at room temperature (20°C) . From threshold up to 85mA, the lasing wavelength is found to vary linearly at 0.009nm/mA, indicating mode-hop-free operation. The device spectra remain v single mode over this range. Single mode emission is found to vary at the rate of 0.08nm/°C around room temperature.
• One possible use of the device of the invention is in an integrated device which has, say, four such laser sources on a single device, with the distributed reflector structures of the four sources being different, such that the integrated device can selectively provide a source at any of four wavelengths .

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• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Optics & Photonics (AREA)
• Semiconductor Lasers (AREA)
• Led Devices (AREA)
• Optical Communication System (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (2)

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Citations (1)

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• 1999
  • 1999-09-08 GB GB9921445A patent/GB2354110A/en not_active Withdrawn
• 2000
  • 2000-09-08 DE DE60002591T patent/DE60002591T2/de not_active Expired - Fee Related
  • 2000-09-08 AU AU70280/00A patent/AU7028000A/en not_active Abandoned
  • 2000-09-08 EP EP00958866A patent/EP1214764B1/en not_active Expired - Lifetime
  • 2000-09-08 WO PCT/GB2000/003483 patent/WO2001018924A1/en not_active Ceased
  • 2000-09-08 AT AT00958866T patent/ATE239990T1/de not_active IP Right Cessation

Patent Citations (1)

Non-Patent Citations (5)

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