摘要:

We report herein the first single‐mode polymer waveguide modulator which can be formed on any surface regardless of its conductivity and refractive index. These include semiconductor, conductor, and insulator surfaces. The tunability of the refractive index of the polymer film allows us to shift the guiding layer from a stepped index profile to a graded index profile. The phase‐matching condition for optical power transfer is achieved through current‐induced index modulation. Thirty‐six dB extinction ratio, which includes 3 dB absorption loss and 33 dB phase‐matched cross coupling, was observed with a current injection density of ∼1.8 &mgr;A/&mgr;m2. Unlike the conventional symmetrical dual channel coupler, the disparity of the collinear waveguide pair provides us with a much larger dynamic range of waveguide dimension suitable for generating the required phase‐matching condition and thus easing the requirement of waveguide fabrication.

ISSN:0003-6951    

DOI:10.1063/1.104437

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The differential gain which is an important parameter for modulation dynamics in semiconductor lasers is evaluated experimentally by measuring the gain coefficient and the carrier lifetime in GaAs/AlGaAs double‐heterostructure (DH) lasers, quantum well (QW) lasers, andp‐modulation‐doped quantum well (p‐MDQW) lasers. The results indicate that the differential gain of the QW laser is 2.4 times as high as that of the DH laser, which is consistent with the theory. In addition, it is found that improvement of the differential gain using thep‐MDQW structure is not so large as that expected by the theory. This result suggests that enhanced energy broadening due to the reduction of the equivalent dephasing time &tgr;eqin, which includes both the dephasing time &tgr;indue to the intraband relaxation and the band tailing effects, significantly affects the gain spectra in thep‐MDQW lasers, which is confirmed by the measurement of the spontaneous emission spectra.

ISSN:0003-6951    

DOI:10.1063/1.104440

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on the first demonstration of pseudomorphic InGaAs single quantum well surface‐emitting lasers (SELs), with etched vertical mirrors and integrated 45° beam deflectors fabricated by ion beam etching. 100‐&mgr;m‐wide broad‐area SELs exhibited a threshold current of 320 mA, a total power of 126 mW, and a total external differential quantum efficiency of 0.09 W/A for a 500‐&mgr;m‐long cavity. The perpendicular far‐field pattern of broad‐area SELs showed a full width at half maximum of ∼20°. The lasers with various types of cavities fabricated from the same wafer were compared. Broad‐area edge‐emitting lasers had a threshold current of 200 mA, a total power of 700 mW, and a total external differential quantum efficiency of 0.52 W/A.

ISSN:0003-6951    

DOI:10.1063/1.104451

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A design is presented for a Ni‐like Ta x‐ray laser which uses less than 1 kJ pump energy. This is in contrast with previous experiments carried out at the Nova two‐beam chamber which have used several kJ pump energy. The main features of the new system are the use of a thin target (30 &mgr;g/cm2Ta), a much lower intensity, and a shorter pulse.

ISSN:0003-6951    

DOI:10.1063/1.104433

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Nonlinear optical measurements in strip‐loaded channel waveguides of poly(4‐BCMU) at 1.319 &mgr;m are reported. Using a pulse‐modulated interferometry method, the intensity‐dependent refractive index is found to have an electronic contribution,n2=(4.8±2.7)×10−8cm2/MW, and an estimated thermal contribution,n2=−(7.9±4.5)×10−11cm2/MW, for 60 pS laser pulses at 76 MHz. The two‐photon absorption coefficient &bgr; is less than 0.25 cm/GW. Figures‐of‐merit suggest that poly(4‐BCMU) has properties desirable for all‐optical devices, but that fabrication losses and thermal effects due to absorption will limit device performance.

ISSN:0003-6951    

DOI:10.1063/1.104434

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

For the first time, high performance GaAs/GaAlAs surface‐emitting lasers with internal 45° micromirrors, which totally reflect and emit the beam from the substrate in junction‐down configuration, have been demonstrated. The 45° and 90° mirrors of the device were fabricated by using ion milling and reactive ion etching techniques, respectively. Typical threshold current density of 440 A/cm2, external differential efficiencies of 52%, and output power in excess of 1 W under quasi‐cw operation have been achieved.

ISSN:0003-6951    

DOI:10.1063/1.104435

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Optical waveguides can be formed in potassium titanyl phosphate (KTiOPO4, KTP) crystals by an ion‐exchange process. Waveguides were fabricated in KTP substrates by exchanging rubidium ions for potassium ions. The resulting refractive index profile was measured as a function of diffusion time and temperature. Based on these characterization measurements, the phase‐matching properties of the planar waveguide for guided‐wave second‐harmonic generation were modeled. Second‐harmonic generation of blue/green light was observed at wavelengths shorter than the bulk phase‐matching limit, in good agreement with the results of numerical modeling.

ISSN:0003-6951    

DOI:10.1063/1.104436

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Monolithic phase‐locked resonant arrays of antiguides, resonant optical‐waveguide (ROW) arrays, have been optimized for efficient in‐phase‐mode operation. Diffraction‐limited, in‐phase‐mode continuous‐wave (cw) operation is obtained from 20‐element uniform arrays to 250 mW output power, with (front facet) external differential quantum efficiencies of 41%. Single longitudinal mode operation is observed below 100 mW cw. In‐phase‐operating devices with and without Talbot‐type spatial filters are compared, and it is found that for ROW arrays Talbot‐type spatial filters are not required.

ISSN:0003-6951    

DOI:10.1063/1.104425

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We describe the power scaling and saturation properties of large‐aperture planar photoconducting antennas which emit and detect ultrashort terahertz electromagnetic pulses. At high optical fluences, the radiated electric field saturates at a value comparable to the bias field in agreement with a simple model of the radiation mechanism.

ISSN:0003-6951    

DOI:10.1063/1.104426

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A wideband integrated optic heterodyning device that utilizes simultaneously a wideband acousto‐optic (AO) Bragg cell and a wide‐angle electro‐optic (EO) Bragg grating lens has been realized, for the first time, in aY‐cut LiNbO3waveguide 1×8×20 mm3in size. The device has demonstrated a bandwidth of 240 MHz centered at 350 MHz and a single‐tone instantaneous and two‐tone third‐order spurious‐free dynamic ranges of 44.6 and 36.0 dB, respectively, at the optical wavelength of 0.6328 &mgr;m. The device suggests a new and simple architecture for wideband integrated optic interferometric rf spectrum analyzers.

ISSN:0003-6951    

DOI:10.1063/1.104427

出版商:AIP    

年代:1991

数据来源: AIP