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22 Feb 1999

Volume 74, Issue 8, pp. 1057-1183

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Optical properties of molecular organic semiconductor thin films under intense electrical excitation

V. G. Kozlov, P. E. Burrows, G. Parthasarathy, and S. R. Forrest

Appl. Phys. Lett. 74, 1057 (1999); http://dx.doi.org/10.1063/1.123480 (3 pages) | Cited 38 times

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Using electro-optical pump and probe measurements, we studied optical properties of a thin film of tris-(8-hydroxyquinoline) aluminum (Alq3) doped with DCM2 laser dye under pulsed injection currents as high as 300 A/cm2. Pump-induced transparency and absorption were observed in the spectral ranges of 570–610 nm and 620–705 nm, respectively. We attribute these optical effects to molecular polarons formed under electrical excitation. Polaron absorption dominates the optical properties of electrically pumped Alq3:DCM2 films in the spectral range where optical gain is anticipated (i.e., from 630 to 700 nm). Polaronic effects may present a significant obstacle for realization of organic diode lasers based on this material system. © 1999 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence
42.70.Jk Polymers and organics
71.38.-k Polarons and electron-phonon interactions
78.40.Me Organic compounds and polymers
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

CaF2:Yb3++Pr3+ codoped waveguides grown by molecular beam epitaxy for 1.3 μm applications

F. Lahoz, E. Daran, G. Lifante, T. Balaji, and A. Muñoz-Yagüe

Appl. Phys. Lett. 74, 1060 (1999); http://dx.doi.org/10.1063/1.123481 (3 pages) | Cited 3 times

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CaF2:Yb3++Pr3+ codoped thin films grown by molecular beam epitaxy have been studied in order to determine their ability to be used for optical amplification in telecommunication devices. The guiding behavior of the layers has been demonstrated and an increase in the refractive index has been measured for increasing Pr3+ and Yb3+ doping levels. Energy transfer between Yb3+ and Pr3+ ions has also been observed with different pump wavelengths. Room temperature 1.3 μm emission of Pr3+ ions has been detected when pumping in the absorption band of Yb3+, where high performance laser diodes already exist. © 1999 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.55.Rz Doped-insulator lasers and other solid state lasers
78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Development of a high-quantum-efficiency single-photon counting system

Shigeki Takeuchi, Jungsang Kim, Yoshihisa Yamamoto, and Henry H. Hogue

Appl. Phys. Lett. 74, 1063 (1999); http://dx.doi.org/10.1063/1.123482 (3 pages) | Cited 133 times

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A high-quantum-efficiency single-photon counting system has been developed. In this system, single photons were detected by a visible light photon counter operated at 6.9 K. The visible light photon counter is a solid state device that makes use of avalanches across a shallow impurity conduction band in silicon. Threefold tight shielding and viewports that worked as infrared blocking filters were used to eliminate the dark count caused by room-temperature radiation. Corrected quantum efficiencies as high as 88.2%±5% (at 694 nm) were observed, which we believe is the highest reported value for a single-photon detector. The dark count increased as the exponential of the quantum efficiency with changing temperature or bias voltage, and was 2.0×104 cps at the highest quantum efficiency. © 1999 American Institute of Physics.
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42.50.Ar Photon statistics and coherence theory
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Ci Filters, zone plates, and polarizers

Mode spacing “anomaly” in InGaN blue lasers

H. X. Jiang and J. Y. Lin

Appl. Phys. Lett. 74, 1066 (1999); http://dx.doi.org/10.1063/1.123483 (3 pages) | Cited 9 times

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An important experimental observation in InGaN laser diodes (LDs), which is not yet fully understood, is that the measured mode spacing of the lasing spectra could be one order of magnitude larger than that “calculated” from the known cavity length. The aim of this letter is to shed light on the nature of the mode spacing “anomaly” in InGaN LDs. We have derived a formula which accurately determines the mode spacing in InGaN LDs. Our analysis has shown that the discrepancy between the “expected” and observed mode spacing is due to the effect of carrier-induced reduction of the refractive index under lasing conditions and this discrepancy decreases and naturally disappears as the threshold carrier density required for lasing decreases. Since the carrier-induced reduction of the refractive index is expected only from an electron–hole plasma state, our results naturally imply that electron–hole plasma recombination provides the optical gain in InGaN LDs, like in all other conventional III–V semiconductor lasers. The implications of our results on the design of nitride optoelectronic devices are also discussed. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Mx High-frequency effects; plasma effects
42.60.By Design of specific laser systems
81.05.Ea III-V semiconductors

Angular filtering of spatial modes in a vertical-cavity surface-emitting laser by a Fabry–Perot étalon

Guoqiang Chen, James R Leger, and Anand Gopinath

Appl. Phys. Lett. 74, 1069 (1999); http://dx.doi.org/10.1063/1.123484 (3 pages) | Cited 3 times

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A low-finesse Fabry–Perot étalon is employed as an angularly selective filter to discriminate against the high-order spatial modes of a vertical-cavity surface-emitting laser (VCSEL) in the near field. Single-transverse-mode operation is obtained over a wide region for a 15 μm diam VCSEL. © 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
42.79.Ci Filters, zone plates, and polarizers
07.60.Ly Interferometers

High-speed >90% quantum-efficiency p–i–n photodiodes with a resonance wavelength adjustable in the 795–835 nm range

Ekmel Özbay, Ïbrahim Kimukin, Necmi Biyikli, Orhan Aytür, Mutlu Gökkavas, Gökhan Ulu, M. Selim Ünlü, Richard P. Mirin, Kris A. Bertness, and David H. Christensen

Appl. Phys. Lett. 74, 1072 (1999); http://dx.doi.org/10.1063/1.123485 (3 pages) | Cited 15 times

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We report GaAs/AlGaAs-based high-speed, high-efficiency, resonant cavity enhanced p–i–n photodiodes. The devices were fabricated by using a microwave-compatible fabrication process. By using a postprocess recess etch, we tuned the resonance wavelength from 835 to 795 nm while keeping the peak efficiencies above 90%. The maximum quantum efficiency was 92% at a resonance wavelength of 823 nm. The photodiode had an experimental setup-limited temporal response of 12 ps. When the system response is deconvolved, the 3 dB bandwidth corresponds to 50 GHz, which is in good agreement with our theoretical calculations. © 1999 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
06.60.Jn High-speed techniques (microsecond to femtosecond)
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
42.86.+b Optical workshop techniques
81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors

High-temperature continuous-wave 3–6.1 μm “W” lasers with diamond-pressure-bond heat sinking

W. W. Bewley, C. L. Felix, I. Vurgaftman, D. W. Stokes, E. H. Aifer, L. J. Olafsen, J. R. Meyer, M. J. Yang, B. V. Shanabrook, H. Lee, R. U. Martinelli, and A. R. Sugg

Appl. Phys. Lett. 74, 1075 (1999); http://dx.doi.org/10.1063/1.123486 (3 pages) | Cited 64 times

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Optically pumped type-II W lasers emitting in the mid-infrared exhibited continuous-wave (cw) operating temperatures of 290 K at λ = 3.0 μm and 210 K at λ = 6.1 μm. Maximum cw output powers for 78 K were 260 mW at λ = 3.1 μm and nearly 50 mW at λ = 5.4 μm. These high maximum temperatures were achieved through the use of a diamond-pressure-bonding technique for heat sinking the semiconductor lasers. The thermal bond, which is accomplished through pressure alone, permits topside optical pumping through the diamond at wavelengths that would be absorbed by the substrate. © 1999 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes

Polarization dynamics in vertical-cavity surface-emitting lasers with optical feedback through a quarter-wave plate

C. Masoller and N. B. Abraham

Appl. Phys. Lett. 74, 1078 (1999); http://dx.doi.org/10.1063/1.123487 (3 pages) | Cited 8 times

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Square-wave switching of the intensities of the orthogonal linearly polarized components of the output of a vertical-cavity surface-emitting laser (VCSEL) found previously in experiments with polarization-changing optical feedback, is not found in rate equation models incorporating only birefringence and gain anisotropy, but is found in the model for VCSELs developed by San Miguel, Feng, and Moloney [M. San Miguel, Q. Feng, and J. V. Moloney, Phys. Rev. A 52, 1729 (1995)]. The dynamics is sensitive to both the feedback strength and the relaxation rate of the magnetization in the quantum well sublevels. © 1999 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.25.Ja Polarization
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