摘要:

A mechanism for sustaining population inversions in contact charge‐transfer complexes in which the ground electronic state is not bound is described. The mechanism relies on picosecond radiationless depletion of the lower laser state. This generates an inversion even when the ground‐state potential curve, as plotted against the donor‐acceptor distance, is not repulsive vertically below the excited state minimum. Contact charge‐transfer lasers would offer high gain, high‐energy density, and tunable sources of coherent radiation in the uv and visible. A method for pumping such a laser is examined and applied to the pyrrole‐oxygen complex. A rate equation analysis is done and estimates for gain and energy density are presented.

ISSN:0021-8979    

DOI:10.1063/1.329355

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

In a CO2gasdynamic laser (GDL), a small signal gain and an output of 16 &mgr;m have been theoretically examined in detail by solving the rate equations with the population of each vibrational level against the 9.4‐&mgr;m stimulating field. The eight levels of CO2up to the (001) level including the (110) and the (030) levels, and the 31 reactions involving theV‐Treactions are taken into account in this model. With a 9.4‐&mgr;m [P(14)] pulse of 10‐MW input power, 8‐mm‐diam spot size, and 100‐nsec pulse width, a 16‐&mgr;m [P(15)] pulse of 27‐&mgr;J/pulse/cm3extractable energy and 5.7‐kW maximum power is obtained from an active length of 0.1 m. It indicates that by using aQ‐switch technique, high‐repetition‐rate operation of 200 kHz can produce an average output power of 5 W/cm3. Finally, a 16‐&mgr;m continuous lasing by injecting the 9.4‐&mgr;m beam continuously is analyzed.

ISSN:0021-8979    

DOI:10.1063/1.329356

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Properties of the visible XeF (C→A) photolytically pumped laser system have been investigated in detail. The research covers four main areas: (1) absolute fluorescence intensities from theCandBstates, (2)C→Afluorescence spectra as a function of pressure and buffer gas, (3) gain/absorption measurements from 400–650 nm, and (4) demonstration of tunable laser operation over the 454–525‐nm range. All results reported here indicate that the XeF (C→A) laser could be a highly efficient visible laser system.

ISSN:0021-8979    

DOI:10.1063/1.329357

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Proton bombarded stripe geometry lasers have been actively mode locked in an external cavity consisting of a lens, a Fabry‐Perot etalon, and a mirror. Under optimized conditions, pulses as short as 5.3 psec have been observed from measurement of the second harmonic autocorrelation function. The dependence of the pulse width on external parameters was studied in detail. The pulse widtht1/2decreases with increasing direct current. The functional dependence of the pulse width on current indicates that a saturable absorption mechanism is present in the laser which causes significant pulse shortening. The pulse width decreases with increasing rf current. The pulse width is a sensitive function of the frequency detuning of the applied rf current. The shortest pulses are observed when the applied frequency is less than the round trip frequency of the pulse in the cavity. The frequency dependence of the pulse width was obtained using a long cavity with multiple pulses in the cavity. The shortest pulses occur between 0.9 and 1.4 GHz. The Fabry‐Perot etalon limits the emission to a 1.9‐A˚ spectral band. At optimum mode locking the band is ∼30 A˚ below the peak of the multimode emission obtained without the etalon. The shift of the gain curve to lower enery indicates that additional loss is introduced by the feedback from the external cavity. The experimental results are shown to be in good agreement with a theoretical description of mode locking.

ISSN:0021-8979    

DOI:10.1063/1.329358

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Room‐temperature operation was obtained in a new transverse junction stripe laser with distributed feedback. The wafers were grown by a liquid phase epitaxy/metal‐organic chemical vapor deposition (LPE/MO‐CVD) hybrid technique. These lasers operated stably in a single longitudinal mode at room temperature under pulsed operation. The temperature dependence of lasing wavelength wasd&lgr;/dT= 0.63 A˚/°C.

ISSN:0021-8979    

DOI:10.1063/1.329359

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Room‐temperature quasi cw lasing at 1.06 &mgr;m was obtained in Li‐(La1−x−yNdxCry) ‐phosphate glass. Thresholds as low as 1 mW and slope efficiencies up to 18% have been measured. Cross pumping of Nd3+(x= 0.3) via Cr3+(y= 0.03) yields a transfer efficiency of 0.45. For broadband pump sources, the spectral factor of merit (2.3) raises the slope efficiency over those of Nd3+‐only doped laser glasses.

ISSN:0021-8979    

DOI:10.1063/1.329369

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Spontaneous emission spectra and intensity measurements are made on buried heterostructure lasers with transparent windows above the active stripe. The bias voltageV, where eV is the separation of quasi‐Fermi levels, is determined from spectral measurements. The total luminescence intensity increases as exp(eV/nkT), wherenchanges from 1.0 to about 2 asVincreases from 1.3 V to the threshold voltage of 1.415 V. The change innis due primarily to saturation of the low‐energy electron states as a result of electron degeneracy. The spectral determination of bias voltage is justified by the close agreement between the threshold voltage determined by spectral analysis and the voltage determined by extrapolation of directly measured light versus voltage data. Calibration of the absolute radiative rate with optical absorption data yields a predicted radiative recombination current ofJth/d≊5.8 kA cm−2 &mgr;m−1, in reasonable agreement with empirical threshold data.

ISSN:0021-8979    

DOI:10.1063/1.329370

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The refractive index change caused by changes in the absorption edge of GaAs is determined by analysis of the spontaneous emission spectrum of a buried heterostructure window laser. The spontaneous emission spectrum is converted to a gain spectrum from which changes in the imaginary part of the refractive index can be calculated as the laser is excited from low current up to threshold. The real change in refractive index is then determined by a Kramers‐Kronig transformation. The change in refractive indexn′ of the GaAs active layer is slightly sublinear with minority carrier densitync. At the laser line, including the calculated contribution of free carriers, &Dgr;n′ = −0.025±0.005 anddn′/dnc= −(1.8±0.4)×10−20cm3in lasers with carrier densities at threshold estimated as 1.02×1018cm−3. Near threshold, the ratio of the change in the real index to the change in the imaginary index is about 6.2.

ISSN:0021-8979    

DOI:10.1063/1.329371

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Qualified GaAlAs/GaAs oxide isolated stripe geometry DH lasers, degraded at temperatures up to 90 °C, have been examined using the cathodoluminescence (CL) and electron beam induced current (EBIC) modes of the scanning electron microscope, and by transmission electron microscopy in a 1‐MeV TEM. The main features observed in the EBIC and CL images in the plane of the heterojunction of the degraded lasers were bright and dark bands running parallel to the stripe, together with brightened mottled regions extending well outside. The separation of the bands and the extent of the mottled region is dependent on the width of the stripe. This general pattern is modified considerably near to the facets of the lasers. Calculations of strain profiles for the different laser types suggested that these phenomena can be explained in terms of a model of operation induced, strain enhanced, defect migration. Small dislocation loops seen at the edges of the stripe, using transmission electron microscopy appear to support this model.

ISSN:0021-8979    

DOI:10.1063/1.329372

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A new type of middle‐infrared optical fiber is proposed in which oxide glass is used as the cladding material to define a hollow core. Several kinds of oxide glasses have refractive indices lower than unity in the frequency range near 1000 cm−1due to the nearby reasonance of molecular vibration; hence due to the total reflection of the incident laser light from air to the oxide‐glass surface, it is expected that the hollow‐core optical fiber made with the glass functioning as the cladding will exhibit small transmission loss. A preliminary experiment on a 1‐mm‐inner diam hollow‐core Pb glass optical fiber shows its loss to be 7.7 dB/m at 940 cm−1for CO2laser light.

ISSN:0021-8979    

DOI:10.1063/1.329373

出版商:AIP    

年代:1981

数据来源: AIP