摘要:

A type of adaptive correlation filter for processing the speckle pattern emerging from an interference fiber-optic sensor is proposed. This filter is simple and self-adjustable, operating on the base of the photorefractive fanning effect. Experiments carried out with aBi12TiO20crystal and multimode optical fiber demonstrate high sensitivity and long-term stability of the sensor. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121974

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The influence of the morphology on the light emission properties of vacuum-deposited polycrystalline oligo(p-phenylene vinylene) thin films under intense laser excitation was studied. The morphology of the thin films was varied by annealing just below the first melting point (crystal-mesophase transition) and by crystallization from the isotropic melt. Amplified spontaneous emission occurred within the individual domains and was only observed when the domain size was increased by thermal treatment. The amplified spontaneous emission threshold for the melt-crystallized thin films was found to be comparable to that for conjugated polymer thin films. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121975

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Optically and electrically pumped infrared lasers based on intersubband transitions in InAs/GaSb/AlAsSb quantum wells are modeled in detail. The large conduction-band offset of the AlAsSb barriers with respect to the InAs wells allows the lasing wavelength to be shortened to at least 1.9 &mgr;m. Furthermore, the small InAs electron mass results in longer phonon-limited lifetimes in the upper lasing subband as well as larger dipole matrix elements. This leads to the prediction of lower threshold currents, and hence, higher cw operating temperatures than for quantum cascade lasers based on the InGaAs/InAlAs/InP system. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121976

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We demonstrate a compact source of ultraviolet single-frequency pulses with high average output power realized by subsequent single-pass frequency doubling and quadrupling of a diode-pumped passivelyQ-switched miniature Nd:YAG ring laser. Pulse widths of 2 ns (full width at half maximum), 20 &mgr;J single pulse energy, and 10 kW peak power are achieved at a wavelength of 266 nm with kilohertz repetition rates. A single-pass energy conversion efficiency of 22&percent; with respect to the fundamental light at 1064 nm and an overall efficiency of 2.8&percent; with respect to the diode pump power are obtained. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121977

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have measured the noise characteristics of single-mode oxide confined surface emitting vertical cavity laser diodes. For pumping levels of more than 3.5 times threshold current, the relative intensity noise is below −150 dB/Hz up to 5 GHz at output powers near 1 mW. For various frequencies, we observe sub-Poissonian noise. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121978

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A simple analytical model of frequency-modulation (FM) laser operation is proposed in terms of a master equation time-domain description. The analysis is capable of capturing the main experimental features of FM oscillation, including the dependence of modulation depth on cavity parameters, distortion effects induced by finite cavity gain bandwidth, and transition to FM mode-locking operation. Experimental results for a FM erbium–ytterbium–glass laser show good agreement with the theoretical predictions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121979

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report THz emission of hot-holes inp-type silicon doped with a boron acceptor concentration ofNA=1.5×1015 cm−3.We apply crossed electric(E)and magnetic(B)fields to the crystal cooled to liquid helium temperature. Optical gain is found for field ratiosE/Bin the range0.5–1 kV cm−1 T−1.We calculate optical gain spectra in Si and identify possible laser transitions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121980

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Mode selectivity of an air-post index-guided vertical-cavity surface-emitting laser structure operating at 1550 nm is investigated using a full-vector Maxwell-equation solver with a finite-difference time-domain method. The resonance wavelengths, quality factors, and spatial field distributions are calculated for the three lowest-order modes. Transverse-mode competition is quantitatively described as a function of the cavity size and the pillar etch depth. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121981

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We show that doping of the transport layers can strikingly improve the properties of organic light emitting diodes (OLEDs). The electroluminescence onset voltage of diodes containing an vanadyl–phthalocyanine (VOPc) hole transport layer intentionally doped with tetrafluorotetracyano-quinodimethan(F4-TCNQ)is reduced by up to an order of magnitude compared to OLED with undoped VOPc. The improved properties of our devices can be explained by the improved conductivity and better injection for a doped transport layer. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121982

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present an investigation of current-induced heating in polymer light emitting diodes. Using short electrical pulse measurements, we were able to quantify the temperature rise in the active region. We consider that heating effects play a major role in limiting the maximum efficiency of devices and in initiating degradation mechanisms. Heating and heat sinking are also discussed in the context of electrically pumped polymer lasers. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121983

出版商:AIP    

年代:1998

数据来源: AIP