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Sample Grating Distributed Feedback Quantum Cascade Laser Array.

Yan FL, Zhang JC, Liu CW, Zhuo N, Liu F, Zhai SQ, Wang ZG - Nanoscale Res Lett (2015)

Bottom Line: A sample grating distributed feedback quantum cascade laser array aim at broad tunability and enhanced side mode suppression ratios is presented.Utilizing a sample grating dependence on emission wavelength and epitaxial side down bonding technique, the array of laser ridges exhibited three separated single mode emissions centered at 4.760, 4.721, and 4.711 μm respectively, in continuous wave at room temperature.Side mode suppression ratios of >35 dB and continuous wave output powers of >10 mW per laser ridge were obtained.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China. flyan2012@semi.ac.cn.

ABSTRACT
A sample grating distributed feedback quantum cascade laser array aim at broad tunability and enhanced side mode suppression ratios is presented. Utilizing a sample grating dependence on emission wavelength and epitaxial side down bonding technique, the array of laser ridges exhibited three separated single mode emissions centered at 4.760, 4.721, and 4.711 μm respectively, in continuous wave at room temperature. Side mode suppression ratios of >35 dB and continuous wave output powers of >10 mW per laser ridge were obtained.

No MeSH data available.


Related in: MedlinePlus

The schematics of a the DFB-QCL array is epitaxial side down bonded on a patterned AlN submount. b The optical microscope image of a sample grating DFB ridge, and Z is the sampled period
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Fig1: The schematics of a the DFB-QCL array is epitaxial side down bonded on a patterned AlN submount. b The optical microscope image of a sample grating DFB ridge, and Z is the sampled period

Mentions: The QCL structure used in this letter, emitting at λ ~4.6 μm, is based on an In0.669Ga0.331As/In0.362Al0.638As so called double-phonon resonance design. The epitaxial growth and layer structure are identical to those given in ref. [13]. Device fabrication started with the definition of a sample DFB grating on upper InGaAs layer, as is similar to ref. [14]. The MBE-grown top cladding was first removed down to the upper InGaAs layer. Then, the based Bragg grating with a period of 0.701 μm and duty cycle (the ratio of grating peak to based grating period Λ) of 45 % was defined using holographic lithography technique. Three separate sampling periods (namely 9.9, 11.3, and 12.1 μm, respectively) with the same duty cycle (the ratio of grating area to sampling period) of 50 % were formed by the conventional optical photolithography and transferred by wet chemical etching to the depth of about 150 nm. The sampled grating of one DFB ridge is shown in Fig. 1b. Then, a 3-μm low-doped (Si, 2.2 × 1016 cm−3) InP layer, followed by a 0.15-μm gradually doped (Si, 1 × 1017 to 3 × 1017 cm−3) InP layer, and a 0.6-μm highly doped InP (Si, 5 × 1018 cm−3) cladding layer were accomplished in sequence as the upper cladding by metal organic vapor phase epitaxy (MOVPE) regrowth. Then, the DFB ridges, with a mean core width of 12 μm and spaced 170 μm apart, were processed using optical photolithography and nonselective wet chemical etching. The bottom and sidewalls of the DFB ridges were passivated with a 450-nm-thick SiO2 layer by chemical vapor deposition. Then, 40/250-nm-thick Ti/Au contact layers were evaporated by electron beam evaporation, followed by a 4-μm-thick electroplated gold layer. The 50-μm-wide electrical isolation trenches between adjacent DFB ridges were defined by wet etching of Au/Ti layers. After thinning the substrate down to about 120 μm, the backside of the wafer was deposited with Ge/Au/Ni/Au metals as substrate contact layer. The waveguide was then cleaved to 2-mm-long cavities, and the high reflectivity (HR) coating consisting of Al2O3/Ti/Au/Ti/Al2O3 (200/10/10/100 nm) was evaporated on the back facet. The entire laser size was about 1.6 mm × 2 mm.Fig. 1


Sample Grating Distributed Feedback Quantum Cascade Laser Array.

Yan FL, Zhang JC, Liu CW, Zhuo N, Liu F, Zhai SQ, Wang ZG - Nanoscale Res Lett (2015)

The schematics of a the DFB-QCL array is epitaxial side down bonded on a patterned AlN submount. b The optical microscope image of a sample grating DFB ridge, and Z is the sampled period
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608948&req=5

Fig1: The schematics of a the DFB-QCL array is epitaxial side down bonded on a patterned AlN submount. b The optical microscope image of a sample grating DFB ridge, and Z is the sampled period
Mentions: The QCL structure used in this letter, emitting at λ ~4.6 μm, is based on an In0.669Ga0.331As/In0.362Al0.638As so called double-phonon resonance design. The epitaxial growth and layer structure are identical to those given in ref. [13]. Device fabrication started with the definition of a sample DFB grating on upper InGaAs layer, as is similar to ref. [14]. The MBE-grown top cladding was first removed down to the upper InGaAs layer. Then, the based Bragg grating with a period of 0.701 μm and duty cycle (the ratio of grating peak to based grating period Λ) of 45 % was defined using holographic lithography technique. Three separate sampling periods (namely 9.9, 11.3, and 12.1 μm, respectively) with the same duty cycle (the ratio of grating area to sampling period) of 50 % were formed by the conventional optical photolithography and transferred by wet chemical etching to the depth of about 150 nm. The sampled grating of one DFB ridge is shown in Fig. 1b. Then, a 3-μm low-doped (Si, 2.2 × 1016 cm−3) InP layer, followed by a 0.15-μm gradually doped (Si, 1 × 1017 to 3 × 1017 cm−3) InP layer, and a 0.6-μm highly doped InP (Si, 5 × 1018 cm−3) cladding layer were accomplished in sequence as the upper cladding by metal organic vapor phase epitaxy (MOVPE) regrowth. Then, the DFB ridges, with a mean core width of 12 μm and spaced 170 μm apart, were processed using optical photolithography and nonselective wet chemical etching. The bottom and sidewalls of the DFB ridges were passivated with a 450-nm-thick SiO2 layer by chemical vapor deposition. Then, 40/250-nm-thick Ti/Au contact layers were evaporated by electron beam evaporation, followed by a 4-μm-thick electroplated gold layer. The 50-μm-wide electrical isolation trenches between adjacent DFB ridges were defined by wet etching of Au/Ti layers. After thinning the substrate down to about 120 μm, the backside of the wafer was deposited with Ge/Au/Ni/Au metals as substrate contact layer. The waveguide was then cleaved to 2-mm-long cavities, and the high reflectivity (HR) coating consisting of Al2O3/Ti/Au/Ti/Al2O3 (200/10/10/100 nm) was evaporated on the back facet. The entire laser size was about 1.6 mm × 2 mm.Fig. 1

Bottom Line: A sample grating distributed feedback quantum cascade laser array aim at broad tunability and enhanced side mode suppression ratios is presented.Utilizing a sample grating dependence on emission wavelength and epitaxial side down bonding technique, the array of laser ridges exhibited three separated single mode emissions centered at 4.760, 4.721, and 4.711 μm respectively, in continuous wave at room temperature.Side mode suppression ratios of >35 dB and continuous wave output powers of >10 mW per laser ridge were obtained.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China. flyan2012@semi.ac.cn.

ABSTRACT
A sample grating distributed feedback quantum cascade laser array aim at broad tunability and enhanced side mode suppression ratios is presented. Utilizing a sample grating dependence on emission wavelength and epitaxial side down bonding technique, the array of laser ridges exhibited three separated single mode emissions centered at 4.760, 4.721, and 4.711 μm respectively, in continuous wave at room temperature. Side mode suppression ratios of >35 dB and continuous wave output powers of >10 mW per laser ridge were obtained.

No MeSH data available.


Related in: MedlinePlus