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10 Mar 2008

Volume 92, Issue 10, Articles (10xxxx)

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Appl. Phys. Lett. 92, 102101 (2008); http://dx.doi.org/10.1063/1.2890735 (3 pages)

Qing Wan, Jin Huang, Zhong Xie, Taihong Wang, Eric N. Dattoli, and Wei Lu
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High performance of GaN thin films grown on sapphire substrates coated with a silica-submicron-sphere monolayer film

Kazumasa Ueda, Yoshihiko Tsuchida, Nobuhiro Hagura, Ferry Iskandar, Kikuo Okuyama, and Yoshiyuki Endo

Appl. Phys. Lett. 92, 101101 (2008); http://dx.doi.org/10.1063/1.2891067 (3 pages) | Cited 5 times

Online Publication Date: 10 March 2008

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A high-performance, GaN-based light emitting diode (LED) was prepared using a metal organic chemical vapor deposition method on a silica-sphere, monolayer-coated sapphire substrate. Various surface coverage ratios of the silica submicron spheres with diameters ranging from 300 to 550 nm were deposited on the sapphire substrate using a spin-coating method. The LED output power was increased 2.5-fold compared with the LED constructed without silica spheres and uniform light distribution was achieved. In addition, LED output power was dependent on silica-sphere size and surface coverage of the substrates.
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68.55.ag Semiconductors
85.60.Jb Light-emitting devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Broadside coupling to long-range surface plasmons using an angle-cleaved optical fiber

Robert Charbonneau, Ewa Lisicka-Shrzek, and Pierre Berini

Appl. Phys. Lett. 92, 101102 (2008); http://dx.doi.org/10.1063/1.2892678 (3 pages) | Cited 8 times

Online Publication Date: 10 March 2008

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A technique for evanescent broadside coupling to surface plasmons is described and demonstrated. The technique makes use of a polarization maintaining optical fiber cleaved at a steep angle and positioned near the structure to be excited such that the slow mode of the fiber couples evanescently to the surface plasmon propagating thereon. The technique is applied to excite long-range surface plasmons on a metal stripe supported by a freestanding dielectric membrane. The technique should be useful for coupling to other plasmonic or dielectric waveguides, and for optical wafer probing.
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42.81.Qb Fiber waveguides, couplers, and arrays
42.81.Gs Birefringence, polarization

Characteristics of long wavelength InGaN quantum well laser diodes

K. S. Kim, J. K. Son, S. N. Lee, Y. J. Sung, H. S. Paek, H. K. Kim, M. Y. Kim, K. H. Ha, H. Y. Ryu, O. H. Nam, T. Jang, and Y. J. Park

Appl. Phys. Lett. 92, 101103 (2008); http://dx.doi.org/10.1063/1.2892634 (3 pages) | Cited 21 times

Online Publication Date: 10 March 2008

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We demonstrated the long wavelength (485 nm) lasing of InGaN laser diodes under continuous wave condition at room temperature over 10 mW. Two InGaN laser structures were adapted with different indium composition for InGaN optical confinement layers (OCLs) below quantum wells. The blue shift of electroluminescence (EL) was reduced in InGaN laser diodes grown on 3% In concentration in InGaN OCL compared with 1.5% In concentration in InGaN OCL. The EL peak for laser diode with 3% In concentration in InGaN OCL occurs at longer wavelength for all current levels compared to the laser with 1.5% In concentration in InGaN OCL. In addition, the laterally nonuniform InGaN wells grown on 1.5% In concentration in InGaN OCL was verified by the cross-sectional view of InGaN active layer using high-resolution transmission electron microscopy.
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42.55.Px Semiconductor lasers; laser diodes

Improvements in a-plane GaN crystal quality by a two-step growth process

J. L. Hollander, M. J. Kappers, C. McAleese, and C. J. Humphreys

Appl. Phys. Lett. 92, 101104 (2008); http://dx.doi.org/10.1063/1.2830023 (3 pages) | Cited 40 times

Online Publication Date: 10 March 2008

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Nonpolar (11math0) a-plane GaN films have been grown by metal-organic vapor deposition on r-plane (1math02) sapphire. Lateral growth is favored using a low V:III ratio resulting in films with a smooth surface, while pitted films are grown at a high V:III ratio indicating preferential on-axis growth. High-resolution x-ray diffraction analysis of both film types showed a strong anisotropy in the peak width of the symmetric omega rocking curve with respect to the in-plane orientation, phi. In-plane isotropic behavior of crystallinity with overall reduced omega full width at half maximum values was achieved when the growth was initiated at a high V:III ratio before reducing the V:III ratio for film coalescence. An improvement of crystal quality through initial surface roughening was equally realized by the incorporation of partial-coverage SiNx interlayers.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Room temperature continuous wave operation of quantum cascade lasers with watt-level optical power

Y. Bai, S. R. Darvish, S. Slivken, W. Zhang, A. Evans, J. Nguyen, and M. Razeghi

Appl. Phys. Lett. 92, 101105 (2008); http://dx.doi.org/10.1063/1.2894569 (3 pages) | Cited 49 times

Online Publication Date: 10 March 2008

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We demonstrate quantum cascade lasers at an emitting wavelength of 4.6 μm, which are capable of room temperature, high power continuous wave (cw) operation. Buried ridge geometry with a width of 9.8 μm was utilized. A device with a 3 mm cavity length that was epilayer-down bonded on a diamond submount exhibited a maximum output power of 1.3 W at room temperature in cw operation. The maximum output power at 80 K was measured to be 4 W, with a wall plug efficiency of 27%.
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42.55.Px Semiconductor lasers; laser diodes

Optical property and spectroscopy studies on the explosive 2,4,6-trinitro-1,3,5-trihydroxybenzene in the terahertz range

Qing-li Zhou, Cun-lin Zhang, Kai-jun Mu, Bin Jin, Liang-liang Zhang, Wei-wei Li, and Rui-shu Feng

Appl. Phys. Lett. 92, 101106 (2008); http://dx.doi.org/10.1063/1.2895638 (3 pages) | Cited 5 times

Online Publication Date: 10 March 2008

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Using the terahertz time-domain spectroscopy, the complex refraction index and dielectric function of the pure 2,4,6-trinitro-1,3,5-trihydroxybenzene (TNPG) are calculated with the obtained parameters of the pure polyethylene (PE) and a mixture of TNPG and PE based on the Bruggeman effective medium theory. The theoretical investigation consistent with the experimental data in the vibration spectra of TNPG is presented in the range of 0.2–2.5 THz. The results reveal that the two absorption features identified as the fingerprint of TNPG in our studied range are mainly dominated by the intramolecular collective vibration modes.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
77.22.Ch Permittivity (dielectric function)
78.30.Jw Organic compounds, polymers
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Experimental study of the output dynamics of intracavity frequency doubled optically pumped semiconductor disk lasers

René Hartke, Valery Baev, Kai Seger, Oliver Back, Ernst Heumann, Günter Huber, Michael Kühnelt, and Ulrich Steegmüller

Appl. Phys. Lett. 92, 101107 (2008); http://dx.doi.org/10.1063/1.2895642 (3 pages) | Cited 3 times

Online Publication Date: 11 March 2008

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The dynamic behavior of the continuous wave output of an intracavity frequency doubled optically pumped semiconductor disk laser is described. These lasers typically exhibit stable emission. The reasons are found to be the tendency to single-mode operation and the high gain coupling of different modes due to an extremely short gain medium and the resonant periodic gain structure. A dependence of the fluctuation amplitude on gain decoupling of different fundamental modes is demonstrated. With the presented laser setup, more than 80% of conversion efficiency with respect to the available fundamental power has been achieved.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics

Demonstration of transverse-magnetic dominant gain in quantum dot semiconductor optical amplifiers

Nami Yasuoka, Kenichi Kawaguchi, Hiroji Ebe, Tomoyuki Akiyama, Mitsuru Ekawa, Shinsuke Tanaka, Ken Morito, Ayahito Uetake, Mitsuru Sugawara, and Yasuhiko Arakawa

Appl. Phys. Lett. 92, 101108 (2008); http://dx.doi.org/10.1063/1.2883978 (3 pages) | Cited 13 times

Online Publication Date: 11 March 2008

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We demonstrated transverse-magnetic (TM)-mode dominated gain at the 1.5 μm wavelength in semiconductor optical amplifiers (SOAs) with columnar quantum dots (QDs). We show that we can control the polarization dependence of optical gain in QD-SOAs by changing the height and tensile-strained barrier of columnar QDs. The TM mode gain is 17.3 dB and a gain of over 10 dB was attained over a wide wavelength range of 200 nm. The saturation output power is 19.5 dBm at 1.55 μm.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Angular spectrum tailoring in solid immersion microscopy for circuit analysis

S. B. Ippolito, P. Song, D. L. Miles, and J. D. Sylvestri

Appl. Phys. Lett. 92, 101109 (2008); http://dx.doi.org/10.1063/1.2892656 (2 pages) | Cited 10 times

Online Publication Date: 11 March 2008

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We present a technique that involves tailoring the angular spectrum in optical microscopy of silicon integrated circuits, with a solid immersion lens. Spatial light modulation to select only supercritical light at the substrate/dielectric interface yields only evanescent and scattered light in the interconnect layers. We demonstrated the technique in optical excitation microscopy of 65 nm silicon-on-insulator circuits, which enabled localization of a fault during microprocessor development. Acquiring images with and without angular spectrum tailoring allowed longitudinal localization of the electrical response to optical excitation. Lateral registration of electrical response and confocal reflection images to the circuit layout was also significantly improved.
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07.60.Pb Conventional optical microscopes
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Submicron silicon waveguide optical switch driven by microelectromechanical actuator

Erdal Bulgan, Yoshiaki Kanamori, and Kazuhiro Hane

Appl. Phys. Lett. 92, 101110 (2008); http://dx.doi.org/10.1063/1.2892677 (3 pages) | Cited 4 times

Online Publication Date: 11 March 2008

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A submicron silicon waveguide optical switch driven by a microelectromechanical actuator is fabricated. The switch is composed of single-mode silicon input and output waveguides and a movable waveguide suspended by silicon springs. Switching occurs when the air gap between input and output waveguides is closed by displacing the movable waveguide 540±20 nm by an electrostatic comb actuator. The switch, fabricated on a silicon-on-insulator wafer, is monolithic, and active switching region is as small as about 40×60 μm2. An extinction ratio of 15±2 dB is experimentally obtained between switch off and on states at 1.55 μm wavelength.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
85.30.-z Semiconductor devices

Power law carrier dynamics in semiconductor nanocrystals at nanosecond timescales

P. H. Sher, J. M. Smith, P. A. Dalgarno, R. J. Warburton, X. Chen, P. J. Dobson, S. M. Daniels, N. L. Pickett, and P. O’Brien

Appl. Phys. Lett. 92, 101111 (2008); http://dx.doi.org/10.1063/1.2894193 (3 pages) | Cited 16 times

Online Publication Date: 11 March 2008

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We report the observation of power law dynamics on nanosecond to microsecond timescales in the fluorescence decay from semiconductor nanocrystals and draw a comparison between this behavior and power law fluorescence blinking from single nanocrystals. The link is supported by comparison of blinking and lifetime data measured simultaneously from the same nanocrystal. Our results reveal that the power law coefficient changes little over the nine decades in time from 10 ns to 10 s, in contrast with the predictions of some diffusion based models of power law behavior.
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78.55.Et II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.47.jd Time resolved luminescence

Monte Carlo study of GaN versus GaAs terahertz quantum cascade structures

Enrico Bellotti, Kristina Driscoll, Theodore D. Moustakas, and Roberto Paiella

Appl. Phys. Lett. 92, 101112 (2008); http://dx.doi.org/10.1063/1.2894508 (3 pages) | Cited 19 times

Online Publication Date: 11 March 2008

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Due to their large optical phonon energies, nitride semiconductors are promising for the development of terahertz quantum cascade lasers with dramatically improved high-temperature performance relative to existing GaAs devices. Here, we present a rigorous Monte Carlo study of carrier dynamics in two structures based on the same design scheme for emission at 2 THz, consisting of GaN/AlGaN or GaAs/AlGaAs quantum wells. The population inversion and hence the gain coefficient of the nitride device are found to exhibit a much weaker (by a factor of over 3) temperature dependence and to remain large enough for laser action even without cryogenic cooling.
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42.55.Px Semiconductor lasers; laser diodes
81.07.St Quantum wells

Control of quantum-confined Stark effect in InGaN/GaN multiple quantum well active region by p-type layer for III-nitride-based visible light emitting diodes

J.-H. Ryou, W. Lee, J. Limb, D. Yoo, J. P. Liu, R. D. Dupuis, Z. H. Wu, A. M. Fischer, and F. A. Ponce

Appl. Phys. Lett. 92, 101113 (2008); http://dx.doi.org/10.1063/1.2894514 (3 pages) | Cited 16 times

Online Publication Date: 11 March 2008

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We demonstrate the control of the quantum-confined Stark effect in InGaN/GaN quantum wells (QWs), grown along the [0001] direction as part of the active region of visible light emitting diodes (LEDs). The effect can be altered by modifying the strain applied to the active region by the hole injection and contact layers. The optical characteristics and electrostatic potentials of the active region of the visible LEDs with different p-type layers are compared. LEDs with p-InGaN on top of the active region show a reduced blueshift in the peak wavelength with increasing injection current and a lower potential difference across the QW than those with p-GaN layers. The electrostatic potentials across the QW have estimated average values of ∼ 0.8 and ∼ 1.3 MV/cm for the active region of LEDs of current study with p-InGaN and p-GaN layers, respectively.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells
73.63.Hs Quantum wells
72.20.Fr Low-field transport and mobility; piezoresistance

Generating electrically tunable optical vortices by a liquid crystal cell with patterned electrode

Y. J. Liu, X. W. Sun, D. Luo, and Z. Raszewski

Appl. Phys. Lett. 92, 101114 (2008); http://dx.doi.org/10.1063/1.2894521 (3 pages) | Cited 7 times

Online Publication Date: 11 March 2008

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An electrically tunable optical vortex was generated in an antiparallel liquid crystal cell, where one electrode was patterned by a photomask, which is achieved by transferring a computer-generated hologram onto a transparency with a resolution of about 25 μm. When a voltage was applied on the cell, an index modulation was induced due to the realignment of liquid crystal molecules, and then an optical vortex beam was produced. The diffraction efficiency measured was about 27.5%. The device also showed a reasonably fast response time.
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42.40.Jv Computer-generated holograms
42.40.Lx Diffraction efficiency, resolution, and other hologram characteristics
42.40.Eq Holographic optical elements; holographic gratings

Ultraviolet spectra of KPb2Cl5:Er3+

Guohua Jia, Peter A. Tanner, Chaoyang Tu, Jianfu Li, Meng-Yeh Lin, and Bing-Ming Cheng

Appl. Phys. Lett. 92, 101115 (2008); http://dx.doi.org/10.1063/1.2896297 (3 pages) | Cited 3 times

Online Publication Date: 12 March 2008

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The vacuum ultraviolet excitation and ultraviolet-visible emission spectra are reported for the laser and upconverter material KPb2Cl5:Er3+. The low-phonon energies of the host lattice enable, in addition to the ten luminescent states of Er3+ in the visible and infrared spectral regions at room temperature, the observation of a further two luminescent multiplet terms in the ultraviolet spectral region at 10 K. A careful distinction is made between 4f11–4f11 Er3+ transitions and the band to band and Pb2+ transitions.
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78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
78.60.-b Other luminescence and radiative recombination
63.20.-e Phonons in crystal lattices

Time-resolved measurement of the local lattice temperature in terahertz quantum cascade lasers

Miriam S. Vitiello, Gaetano Scamarcio, and Vincenzo Spagnolo

Appl. Phys. Lett. 92, 101116 (2008); http://dx.doi.org/10.1063/1.2894585 (3 pages) | Cited 6 times

Online Publication Date: 12 March 2008

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We measured the time dependence of the local lattice temperature in terahertz quantum cascade lasers with surface plasmon waveguides. The time constants for heat extraction from the active region (0.15–0.29 μs) are approximately ten times shorter than those associated with heat extraction from the substrate, thereby showing the dominant role of the substrate-heat sink coupling. Thermal diffusivities D = 0.052 cm2/s (Ds = 3.9 cm2/s) and thermal diffusion lengths μ = 1.2 μm (μs = 31 μm) in the active region (substrate) have been extracted by fitting the solution of the heat transport equation to the experimental data.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

High spatial resolution fiber-optic Fizeau interferometric strain sensor based on an in-fiber spherical microcavity

Enbang Li, Gang-Ding Peng, and Xin Ding

Appl. Phys. Lett. 92, 101117 (2008); http://dx.doi.org/10.1063/1.2895637 (3 pages) | Cited 7 times

Online Publication Date: 13 March 2008

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We present a fiber-optic Fizeau interferometric strain sensor consisting of an in-fiber spherical microcavity of 39 μm in diameter. The spherical microcavity was formed by splicing a normal single-mode fiber with a hollow-core photonic crystal fiber. We demonstrate that strain sensing can be realized by using the interference between the light signals reflected by the front and rear surfaces of the sphere. Experiments have shown that the strain sensor has a strain sensitivity of 3.36 pm/με and a temperature sensitivity of 1.35 pm/°C.
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07.10.Pz Instruments for strain, force, and torque
42.81.Pa Sensors, gyros
42.70.Qs Photonic bandgap materials

Nearly lattice-matched n, i, and p layers for InGaN p-i-n photodiodes in the 365–500 nm spectral range

E. A. Berkman, N. A. El-Masry, A. Emara, and S. M. Bedair

Appl. Phys. Lett. 92, 101118 (2008); http://dx.doi.org/10.1063/1.2896648 (3 pages) | Cited 5 times

Online Publication Date: 13 March 2008

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We report on nearly lattice-matched grown InGaN based p-i-n photodiodes detecting in the 365–500 nm range with tunable peak responsivity tailored by the i-layer properties. The growth of lattice matched i- and n-InGaN layer leads to improvement in the device performance. This approach produced photodiodes with zero-bias responsivities up to 0.037 A/W at 426 nm, corresponding to 15.5% internal quantum efficiency. The peak responsivity wavelength ranged between 416 and 466 nm, the longest reported for III-N photodiodes. The effects of InN content and i-layer thickness on photodiode properties and performance are discussed.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Kk Junction diodes
85.30.De Semiconductor-device characterization, design, and modeling

Combined nonlinear-optical electric and magnetic field response in a cadmium manganese telluride crystal

Chia-Chu Chen and John F. Whitaker

Appl. Phys. Lett. 92, 101119 (2008); http://dx.doi.org/10.1063/1.2896651 (3 pages) | Cited 3 times

Online Publication Date: 13 March 2008

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Utilizing experimental results, which demonstrate the presence of both Faraday rotation and electric-field-induced linear birefringence in a diluted-magnetic-semiconductor crystal of cadmium manganese telluride (CMT), a single probe that is capable of sensing both electric and magnetic fields independently has been developed. A higher field sensitivity and greater accuracy are observed for the CMT crystal when compared to a lithium tantalate electro-optic crystal and terbium gallium garnet magneto-optic crystal. The linear electro-optic coefficient r41 for CMT has been calculated from electric-field measurements to be 3.5±0.2 pm/V.
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78.20.Fm Birefringence
78.20.Ls Magneto-optical effects
78.20.Jq Electro-optical effects
75.50.Pp Magnetic semiconductors

Back-illuminated separate absorption and multiplication GaN avalanche photodiodes

J. L. Pau, C. Bayram, R. McClintock, M. Razeghi, and D. Silversmith

Appl. Phys. Lett. 92, 101120 (2008); http://dx.doi.org/10.1063/1.2897039 (3 pages) | Cited 7 times

Online Publication Date: 13 March 2008

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The performance of back-illuminated avalanche photodiodes with separate absorption and multiplication regions is presented. Devices with an active area of 225 μm2 show a maximum multiplication gain of 41 200. The calculation of the noise equivalent power yields a minimum value of 3.3×10−14 W Hz−1/2 at a gain of 3000, increasing to 2.0×10−13 W Hz−1/2 at a gain of 41 200. The broadening of the response edge has been analyzed as a function of bias.
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85.60.Dw Photodiodes; phototransistors; photoresistors

Enhanced broadband near-infrared luminescence and optical amplification in Yb–Bi codoped phosphate glasses

Jian Ruan, E Wu, Heping Zeng, Shifeng Zhou, G. Lakshminarayana, and Jianrong Qiu

Appl. Phys. Lett. 92, 101121 (2008); http://dx.doi.org/10.1063/1.2897292 (3 pages) | Cited 23 times

Online Publication Date: 13 March 2008

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Yb–Bi codoped phosphate glass was prepared and its properties were compared with Bi-doped phosphate glass. The broadband infrared luminescence intensity from Yb–Bi codoped glass was ∼ 32 times stronger than that of Bi-doped glass. The single-pass optical amplification was measured on a traditional two-wave mixing configuration. No optical amplification was observed in Bi-doped glass, while apparent broadband optical amplification between 1272 and 1336 nm was observed from Yb–Bi codoped glass with 980 nm laser diode excitation. The highest gain coefficient at 1272 nm of Yb–Bi codoped glass reached to 2.62 cm−1. Yb–Bi codoped phosphate glass is a promising material for broadband optical amplification.
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78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.43.Fs Glasses

Finesse enhancement in silicon-on-insulator two-ring resonator system

Landobasa Y. M. Tobing, Desmond C. S. Lim, Pieter Dumon, Roel Baets, and Mee-Koy Chin

Appl. Phys. Lett. 92, 101122 (2008); http://dx.doi.org/10.1063/1.2894203 (3 pages) | Cited 8 times

Online Publication Date: 13 March 2008

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We demonstrate experimentally the finesse enhancement in a pair of mutually coupled ring resonators coupled to two buses fabricated in silicon-on-insulator technology, as proposed theoretically in an earlier paper. A finesse close to 100 (or Q = 30 000) is obtained in a two-ring system, with the outer ring double the size of the inner ring, and an external coupling coefficient of 34%. The maximum finesse enhancement relative to the single-ring structure is 14 times, in good agreement with the theoretical prediction.
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42.79.-e Optical elements, devices, and systems

High-power semiconductor disk laser based on InAs/GaAs submonolayer quantum dots

T. D. Germann, A. Strittmatter, J. Pohl, U. W. Pohl, D. Bimberg, J. Rautiainen, M. Guina, and O. G. Okhotnikov

Appl. Phys. Lett. 92, 101123 (2008); http://dx.doi.org/10.1063/1.2898165 (3 pages) | Cited 12 times

Online Publication Date: 13 March 2008

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An optically pumped semiconductor disk laser using submonolayer quantum dots (SML QDs) as gain medium is demonstrated. High-power operation is achieved with stacked InAs/GaAs SML QDs grown by metal-organic vapor-phase epitaxy. Each SML-QD layer is formed from tenfold alternate depositions of nominally 0.5 ML InAs and 2.3 ML GaAs. Resonant periodic gain from a 13-fold nonuniform stack design of SML QDs allows to produce 1.4 W cw at 1034 nm. The disk laser demonstrates the promising potential of SML-QD structures combining properties of QD and quantum-well gain media for high-power applications.
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42.55.Px Semiconductor lasers; laser diodes
81.07.Ta Quantum dots
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
78.67.Hc Quantum dots

Second harmonic generation in ridge Bragg reflection waveguides

Bhavin Bijlani, Payam Abolghasem, and A. S. Helmy

Appl. Phys. Lett. 92, 101124 (2008); http://dx.doi.org/10.1063/1.2894516 (3 pages) | Cited 13 times

Online Publication Date: 13 March 2008

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Monolithic AlGaAs ridge Bragg reflection waveguides are used to achieve exact phase matching in a second harmonic generation experiment for a pump at 1600 nm. Phase-matching bandwidth of 4.5 nm, with a peak internal conversion efficiency of 205%/W cm2, is obtained. This conversion efficiency is comparable to numbers reported for periodically poled lithium niobate. The phase-matching peak was found to redshift with sample temperature providing tunablity at a rate of 0.25 nm/ °C. Possible routes for enhancing the current efficiency levels are also discussed.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

Modulated optical phase conjugation in rhodamine 110 doped boric acid glass saturable absorber thin films

Ramesh C. Sharma, Thomas A. Waigh, and Jagdish P. Singh

Appl. Phys. Lett. 92, 101125 (2008); http://dx.doi.org/10.1063/1.2897307 (3 pages)

Online Publication Date: 14 March 2008

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The optical phase conjugation signal in nearly nondegenerate four wave mixing was studied using a rhodamine 110 doped boric acid glass saturable absorber nonlinear medium. We have demonstrated a narrow band optical filter (2.56±0.15 Hz) using an optical phase conjugation signal in the frequency modulation of a weak probe beam in the presence of two strong counterpropagating pump beams in rhodamine 110 doped boric acid glass thin films (10−4 m). Both the pump beams and the probe beam are at a wavelength of 488 nm (continuous-wave Ar+ laser). The probe beam frequency was detuned with a ramp signal using a piezoelectric transducer mirror.
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42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
42.79.Ci Filters, zone plates, and polarizers
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.79.Hp Optical processors, correlators, and modulators
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