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16 Aug 1999

Volume 75, Issue 7, pp. 885-1026

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Single-mode, single-lobe operation of surface-emitting, second-order distributed feedback lasers

J. Lopez, G. Witjaksono, and D. Botez

Appl. Phys. Lett. 75, 885 (1999); http://dx.doi.org/10.1063/1.124544 (3 pages) | Cited 3 times

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A thin p-cladding InGaAs/InGaP/GaAs laser structure (λ = 0.977 μm) with a second-order Au/air grating (70% duty cycle) and asymmetrically coated (30%, 5% reflectivity) cleaved facets emits in a diffraction-limited (0.11°) single lobe in a direction virtually normal to the chip surface. The near-field pattern corresponds to (grating) phase shifts of 10° and 40° at the low- and high-reflectivity cleaved-mirror facets. An analysis of 30%/0% coated, 500-μm-long devices shows that single-lobe surface emission occurs for a wide variation in grating phase with respect to the high reflectivity mirror, ΔϕHR: 10°–80°. For 99%/0% coated devices, single-lobe emission occurs with relatively uniform near-field intensity profile and external differential quantum efficiency ηd around 20% for ΔϕHR values close to π/4 (i.e., in the 45°–65° range). Single-lobe emission normal to the chip surface (i.e., symmetric-mode lasing) can then be obtained from devices without cleaved mirrors by introducing a phase shift close to π/2 in the center of the second-order grating. For the structure used, a phase shift of 90°–130° in the center of 1-mm-long gratings is found to provide single-lobe surface emission with substantially uniform near-field profile, and ηd values as high as 22%. Increasing the grating-section length increases ηd (e.g., 35% for 1.5-mm-long gratings) at some price in near-field uniformity. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Dj Gratings
42.79.Bh Lenses, prisms and mirrors

White-light-emitting organic electroluminescent devices based on interlayer sequential energy transfer

R. S. Deshpande, V. Bulović, and S. R. Forrest

Appl. Phys. Lett. 75, 888 (1999); http://dx.doi.org/10.1063/1.124250 (3 pages) | Cited 184 times

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We demonstrate efficient, molecular organic white-light-emitting devices using vacuum-deposited thin films of red luminescent [2-methyl-6-[2-(2,3,6,7-tetrahydro-1H, 5H-benzo [ij] quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile (DCM2), doped into blue-emitting 4, 4′ bis [N-1-napthyl-N-phenyl-amino]biphenyl (α-NPD), and green-emitting tris-(8-hydroxyquinolinato) aluminum(III) (AlQ3). The luminescent layers are separated by a hole-blocking layer of 2,9-dimethyl, 4,7-diphenyl, 1,10-phenanthroline (BCP), whose thickness is on the order of a typical Förster transfer radius of 30–40 Å. Excitons formed on α-NPD sequentially transfer their energy via a Förster mechanism to AlQ3 across the BCP layer, and from AlQ3 to DCM2. This interlayer sequential energy transfer results in partial excitation of all three molecular species, thereby producing white light emission. The thickness of the blocking layer and the concentration of DCM2 in α-NPD permit the tuning of the device spectrum to achieve a balanced white emission with Commission Internationale d’Eclairage chromaticity coordinates of (0.33, 0.33). The spectrum is largely insensitive to the drive current, and the devices have a maximum luminance of 13 500 cd/m2. At a luminance of 100 cd/m2, the quantum and power efficiencies are 0.5% and 0.35 lm/W, respectively. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence
71.35.-y Excitons and related phenomena

Compensated dispersion tuning in harmonically mode-locked fiber laser

K. Chan and C. Shu

Appl. Phys. Lett. 75, 891 (1999); http://dx.doi.org/10.1063/1.124545 (3 pages) | Cited 6 times

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Electrical tuning of wavelength has been demonstrated in a harmonically mode-locked fiber laser using a compensated dispersion-tuning approach. The cavity consists of a standard single-mode fiber (SMF) and a dispersion-compensated fiber (DCF), providing equal and opposite group velocity dispersion to wavelength components around 1.55 μm. Tuning is achieved by controlling the delay time between electrical pulse signals applied to two modulators connecting the SMF and the DCF. The tuning relation exhibits a linear characteristic and matches with the calculated result. A 21.5 nm tuning range is obtained with an extinction ratio as high as 47 dB at a constant operating frequency of 1 GHz. © 1999 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Wd Fiber lasers
42.81.Dp Propagation, scattering, and losses; solitons
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Low-threshold optically pumped lasing at 444 nm at room temperature with high characteristic temperature from Be-chalcogenide-based single-quantum-well laser structures

J. H. Chang, M. W. Cho, K. Godo, H. Makino, T. Yao, M. Y. Shen, and T. Goto

Appl. Phys. Lett. 75, 894 (1999); http://dx.doi.org/10.1063/1.124546 (3 pages) | Cited 8 times

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We have achieved low-threshold optically pumped lasing at 444 nm at room temperature with high characteristic temperature (T0) from ZnSe/ZnMgBeSe single-quantum-well structures. The threshold intensity is as low as 15 kW cm−2, while T0 value is as high as 166 K. Lasing is observed up to 473 K. Lasing wavelength of 444 nm at room temperature is the shortest wavelength ever achieved in ZnSe-based laser diode structures. The laser structure includes a single ZnMgBeSe/ZnSe/ZnMgBeSe quantum well with a ZnSe well thickness of 4 nm. The (004) x-ray diffraction rocking curve of the ZnMgBeSe quaternary cladding layers shows a sharp diffraction peak with a full width at half maximum of 21 arcsec which is in contrast to that from a ZnMgSSe cladding layer showing much broader multiple peaks. The observed lasing features are partly ascribed to high crystal quality of the ZnMgBeSe layers and type-I band alignment, as has been supported by photoluminescence in addition to x-ray diffraction measurements. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors

Half-symmetric cavity microelectromechanically tunable vertical cavity surface emitting lasers with single spatial mode operating near 950 nm

Peidong Wang, Parviz Tayebati, Daryoosh Vakhshoori, Chih-Cheng Lu, Masud Azimi, and Robert N. Sacks

Appl. Phys. Lett. 75, 897 (1999); http://dx.doi.org/10.1063/1.124251 (2 pages) | Cited 4 times

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We describe tunable vertical cavity surface emitting lasers with a half-symmetric cavity structure. The cavity is realized by inducing a curvature (R ∼ 300 μm) in the top movable dielectric mirror. This half-symmetric microcavity forces lasing oscillations in a single fundamental spatial mode with a side-mode suppression ratio of >25 dB. Continuous wavelength tuning of 44 nm was achieved microelectromechanically with a tuning voltage of 14 V. The device operates near 950 nm with maximum power output of ∼0.9 mW. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Optically pumped type-II interband terahertz lasers

I. Vurgaftman and J. R. Meyer

Appl. Phys. Lett. 75, 899 (1999); http://dx.doi.org/10.1063/1.124547 (3 pages) | Cited 10 times

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Optically pumped terahertz lasers based on interband transitions in type-II antimonide heterostructures are proposed and modeled in detail. At cryogenic temperatures, the activated nature of the Auger and phonon-assisted mechanisms should provide substantially longer nonradiative lifetimes and higher gains than are attainable with intersubband devices. For emission at λ = 27 μm, pulsed operation is projected up to 60 K, and >25 mW of cw output power is calculated for T = 30 K. At T = 4 K, lasing is expected out to wavelengths as long as 100 μm. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

Large third-order optical nonlinearity in SrBi2Ta2O9 thin films by pulsed laser deposition

W. F. Zhang, M. S. Zhang, Z. Yin, Y. Z. Gu, Z. L. Du, and B. L. Yu

Appl. Phys. Lett. 75, 902 (1999); http://dx.doi.org/10.1063/1.124548 (3 pages) | Cited 23 times

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Well-crystallized SrBi2Ta2O9 (SBT) thin films with good surface morphology were prepared on quartz substrates by the pulsed laser deposition technique at a deposition temperature of 750 °C. The third-order nonlinear optical properties of the films were measured by the Z-scan technique. The magnitude and sign of the nonlinear refractive index n2 were determined, as was the negative sign, which indicated a self-defocusing optical nonlinearity. A nonlinear refractive index as high as 1.9×10−6 esu was displayed in the SBT thin film. These results show that SBT ferroelectric thin films have potential applications in nonlinear optics. © 1999 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Optical properties of three-dimensional photonic crystals based on III–V semiconductors at infrared to near-infrared wavelengths

Susumu Noda, Noritsugu Yamamoto, Hideaki Kobayashi, Makoto Okano, and Katsuhiro Tomoda

Appl. Phys. Lett. 75, 905 (1999); http://dx.doi.org/10.1063/1.124549 (3 pages) | Cited 58 times

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The optical properties of three-dimensional photonic crystals based on III–V semiconductors are investigated. The crystals are constructed by stacking GaAs (or InP) stripes with a wafer-fusion technique to form an asymmetric face-centered-cubic structure. It is shown that a crystal with eight-stacked layers (two units), whose period is 4 μm, has a considerable band-gap effect (∼30 dB attenuation) in the transmission spectrum at infrared wavelengths (5–10 μm), and the band gap is observed independently of the incident angles. Then, a crystal with four-stacked layers with a submicron period is constructed, and a clear band gap (attenuation up to 10 dB) is successfully observed at near-infrared wavelengths (1–1.5 μm). © 1999 American Institute of Physics.
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42.70.Qs Photonic bandgap materials

The dual wavelength Bi-vertical cavity surface-emitting laser

J. F. Carlin, R. P. Stanley, P. Pellandini, U. Oesterle, and M. Ilegems

Appl. Phys. Lett. 75, 908 (1999); http://dx.doi.org/10.1063/1.124550 (3 pages) | Cited 18 times

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We present a monolithically integrated vertical coupled cavity surface-emitting laser diode which exhibits stable laser emission at two design wavelengths simultaneously. The device consists of two slightly asymmetric coupled vertical cavities containing strained InGaAs quantum wells as the gain media. The shorter cavity is pumped electrically. Lasing starts on the short wavelength mode at 927 nm. The laser emission then acts as an optical pump for the quantum wells in the longer cavity and provides additional gain for the long wavelength mode, resulting in a subsequent laser emission at 955 nm. With increasing injection current, the device maintains stable emission at the two wavelengths. The threshold for dual lasing is 4 kA/cm2 and dual lasing is stable over six times the threshold. © 1999 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.82.Cr Fabrication techniques; lithography, pattern transfer
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