摘要:

We report the modulation characteristics of multiple quantum well tunneling injection lasers designed for 0.98 &mgr;m emission wavelength. Electrons are injected into the active region through a single barrier via tunneling. The active region has four quantum wells with different well widths. Improved high frequency performance, compared to similar separate confinement heterostructure lasers, has been demonstrated. The modulation response at 21 GHz is above 0 dB and the extrapolated −3 dB modulation bandwidth is ∼30 GHz under pulsed bias. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117507

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Strongly improved surface emitting laser diodes based on surface mode emission are presented. A first‐order‐grating was utilized for the excitation of the surface modes. This results in an efficient quasi‐single‐beam surface emission with low divergence and a significant narrowing in the emission spectrum. A variation in the emission wavelength of up to 4 nm is achieved by adjusting the surface waveguide thickness, which demonstrates the wavelength selection mechanism of the SME technique. The decisive advantage of the SME laser diodes in comparison to DFB/DBR laser diodes is their high flexibility in fabrication, which makes them very suitable for wavelength division multiplexing applications. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117508

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A multilayered electroluminescent device was constructed with ordered perylene thin films as an emission layer. The epitaxial perylene film was prepared by vapor deposition onto the KCl (001) surface, then removed from the KCl substrate and sandwiched between the hole‐transport layer coated on an indium tin oxide electrode and Al top electrode. In this epitaxial layer, the perylene molecules oriented their molecular planes perpendicular to the electrode surfaces. This epitaxial device emitted an electroluminescence in the longer wavelengths of 560–580 nm due to the ordered dimeric structure. On the other hand, the device with polycrystalline perylene films exhibited an electroluminescence mainly below 500 nm. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117509

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

All‐optical locking of the frequency difference between two laser diodes onto a Raman transition is demonstrated. The properties of Raman‐type polarization spectroscopy are discussed and exemplified in the cases of the 3.036 GHz Raman resonance of the85Rb D2line. The generation of a polarization‐selective Raman resonant optical feedback ensures the Raman optical locking of the slave diode laser onto the master oscillator. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117510

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present a scheme for exploiting the nonresonant second‐order nonlinearities in electro‐optic media to extend the bandwidth of coherent spectroscopy in the far‐infrared using ultrafast laser pulses. Using optical rectification and electro‐optic sampling in ⟨110⟩ ZnTe for the generation and coherent detection of freely propagating THz radiation, respectively, we have demonstrated spectral sensitivity beyond 3 THz. This was accomplished by achieving phase matching for both optical rectification and electro‐optic sampling over a broad range of THz frequencies. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117511

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Asymmetrically confined multiple quantum well laser structures have recently been very successful in reaching high modulation bandwidths up to 26 GHz, reported in the InGaAs/InGaAlAs material system. We have measured the effective carrier transport time in structures of this kind by performing parasitic‐free optical modulation experiments. The result is one specific transport time for each confinement layer width. We show that down to layer widths of about 100 nm this effective time for both types of carriers is given by a pure diffusion process for InGaAs/InGaAlAs. Finally, a diffusion constant for the barrier/confinement carriers results in InGaAlAs material which is in very good agreement with reported mobilities. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117512

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the degree to which the resonances associated with metal island films can be used to enhance the sensitivity of very thin semiconductor photodetectors. The island films can couple incident light into the waveguide modes of the detector, resulting in increased absorption. To characterize the coupling, silver‐, gold‐, and copper‐island layers were formed on the surface of a thin‐film photodetector fabricated in the 0.16 &mgr;m thick silicon layer of a silicon‐on‐insulator (SOI) wafer. The copper islands gave the best result, producing more than an order of magnitude enhancement in the photocurrent for light of wavelength 800 nm. The enhancements appear to be due primarily to coupling between the metal island resonances and the waveguide modes supported by the SOI structure. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117513

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report on the fabrication of photodetectors with a response near 1.3 &mgr;m wavelength using an epitaxial SiGeC alloy grown on a Si substrate. The active absorption layer of the SiGeC/Sipinphotodiode consists of a strained SiGeC alloy with a Ge content of 60% and a thickness of 800 A˚. The device exhibits a peak response at 0.85 &mgr;m with the response extending to 1.3 &mgr;m and a cutoff wavelength at around 1.55 &mgr;m. The photocurrent response of the device versus reverse bias voltage saturates at 0.5 V. The leakage current density at the saturation voltage is 70 pA/&mgr;m2. These results may shed some light on Si‐based SiGeC alloys for photodetector applications in the 1.3–1.55 &mgr;m wavelength range. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117514

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Planar optical waveguides with different refractive indices are made inz‐cut LiNbO3with a dilute proton exchange method using a system of glycerol containing KHSO4and lithium benzoate. The optical second‐order susceptibilities of these waveguides are measured by detecting the 266 nm reflected second‐harmonic signal generated by a 532 nm beam directed onto the waveguide surface. It is found for this kind of waveguides that in the waveguide region all the second‐order susceptibilities take values of at least 90% of the original LiNbO3values for refractive index changes less than ∼0.013 at the 632.8 nm wavelength, whereas the susceptibilities are strongly reduced for larger index changes. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117515

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report on experiments, applying a novel microscopy method for ultrathin‐film characterization which uses the dispersion properties of plasmon surface polaritons (PSP) as a contrast giving mechanism. In contrast to prior methods, we apply white light instead of a laser for resonant PSP excitation. For a given incident angle and an area of given thickness, a narrow spectral band of the incident light is at resonance for PSP excitation. Therefore, we obtain images with areas of different thickness appearing in different color. As an example, we present microscopic images taken from a thin Cu–phthalocyanine film, evaporated onto solid support through a mask. In addition, we compare the obtained images to theoretical considerations on the contrast mechanism. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117516

出版商:AIP    

年代:1996

数据来源: AIP