摘要:

The possibility of obtaining high‐power 16‐&mgr;m radiation from a conventional gasdynamic CO2laser (GDL) has been evaluated theoretically by means of a modified Anderson’s time‐dependent method. The analysis showed that up to 2.5% cm−1gain can be achieved on the P(15) line of the (0200)–(0110) transition by injecting a fast 9.4‐&mgr;m pulse at a position 15 cm downstream of the nozzle throat to populate the upper laser level. For a gas mixture of CO2:N2:H2=20:73:7(%) and a nozzle area ratio of 100, the optimum reservoir temperature and pressure were calculated to be 1200 K and 15 atm. Because of its high repetition rate and high average‐power capabilities, such a conventional GDL could easily provide the power levels required for industrial applications of 16‐&mgr;m radiation.

ISSN:0021-8979    

DOI:10.1063/1.328222

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We have done a comparative examination of two sets of lasers, one set exhibiting a light jump and unusually low pulsation frequencies and another set of ’’normal’’ lasers which do not show these phenomena. Our characterization involved measurements of the near field and far field, the emission spectrum versus current, and the pulsation frequency versus current. These measurements did not reveal any major differences between the two types of lasers except that the pulsation frequencies tend to be lower when light jumps are present. In addition, the laser facets were stained with a diluteA/Betch and inspected with a scanning electron microscope. This showed that the distinction between the two types of lasers may be the position of the tail of the proton bombardment with respect to the active layer.

ISSN:0021-8979    

DOI:10.1063/1.328223

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The 70 °C dry nitrogen ambient, continuously operating, lasing lifetimes of 8‐ and 12‐&mgr;m stripe width proton‐bombardment‐delineated double heterostructure (Al,Ga)As lasers are compared. The different stripe‐width lasers are found not to exhibit significant lifetime differences for (slice dependent) median lifetimes less than about 1000 h at 70 °C. However, for median lifetimes greater than this the wider stripe lasers are statistically longer lived. In companion experiments the lasing lifetimes of devices with deep and shallow proton bombardment (protons penetrating, and not penetrating the active volume) have been found to be similar, with the possible exception of very long‐lived devices. In the latter case shallow bombarded devices may be superior. More experiments will be required to establish a causal relationship, if it exists, between proton damage in or near the active volume and laser lifetime.

ISSN:0021-8979    

DOI:10.1063/1.328224

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Data are presented showing that high quality visible‐spectrum multiple‐ quantum‐well In1−x′Gax′P1−z′Asz′‐ In1−xGaxP1−zAsz(x≳x′,z≳z′) heterostructures can be grown on GaAs1−yPy(y∼0.30) substrates by a mechanized computer‐controlled liquid phase epitaxial process. Undoped visible‐spectrum (6600–6000 A˚) heterostructures with as many as 12 uniform coupled quantum wells (Lz∼160 A˚) have been grown and have been examined (77 and 300 K) via photopumping. Phonon participation in the recombination process is dominant in these quaternary quantum‐well heterostructures and lowers the recombination energy by as much as 2?&ohgr;LO(InGaPAs)∼68 meV below the lowest (n=1,n′=1′) confined‐particle transitions.

ISSN:0021-8979    

DOI:10.1063/1.328225

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Temperature dependence of threshold current in InGaAsP/InP double‐heterostructure (DH) lasers was studied from the standpoint of the effect of carrier leakage from the quaternary active region into the InP confining layers. The carrier‐confinement coefficient, defined as the ratio of confined carriers to total injected carriers in the active region, was connected with other oscillation characteristics such as emission efficiency, carrier lifetime, and internal quantum efficiency in three different ways. These variations, as a function of ambient temperature, were measured and the temperature variation of the carrier‐confinement coefficient was evaluated and compared with that of threshold current. These results demonstrated that the carrier leakage was the dominant mechanism on temperature dependence of threshold current in InGaAsP/InP DH lasers. Moreover, we too discussed the other possibilities such as the effects of interfacial recombination at heterojunctions and laser parameters.

ISSN:0021-8979    

DOI:10.1063/1.328226

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

New experimental results on self‐sustained pulsations in semiconductor lasers are presented and compared with theoretical predictions. These results show that laser diodes with high external differential quantum efficiency (&eegr;ext) and low coefficient of spontaneous emission coupled into lasing modes (&bgr;) have a significantly higher probability of developing pulsations, which is in good agreement with theoretical predictions. Furthermore, these results provide strong evidence that the laser cavity contains defects which act as optically saturable absorbing centers. These may be incorporated into the active layer of the laser during crystal growth and/or subsequent fabrication.

ISSN:0021-8979    

DOI:10.1063/1.328227

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A new type of AlGaAs injection laser is described. The structure consists of alternatingp‐ andn‐type layers of GaAs and Alx Ga1−xAs . The electrical mode of operation of the device is that of a Shockley diode (SCR). Optically the device operates as a large optical cavity. Single transverse mode operation was observed with optical cavities larger than 4 &mgr;m.

ISSN:0021-8979    

DOI:10.1063/1.328228

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Laser diodes modelocked to date are gain modulated in an external resonator. The reflection from the diode face internal to the resonator causes a dependence of gain upon frequency that cannot be described by a simple bell‐shaped function. Previous analyses treating modelocking by modulation of loss are generalized to treat modulation of gain with a general frequency dependence. We arrive at a limit on pulse width achievable with gain modulation of a laser diode in an external resonator and evaluate the limit for typical parameters.

ISSN:0021-8979    

DOI:10.1063/1.328253

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Wavelength multiplexer for single‐mode optical communication is reported. The multiplexer is made of all single‐mode fibers and exhibits excellent stability. The separation between the multiplexed wavelengths was about 3.5 nm.

ISSN:0021-8979    

DOI:10.1063/1.328254

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The photoacoustic signal from a finite cylindrical solid sample under excitation by an arbitrary incident source is derived and is in general a complicated function of the beam profile, optical, thermal, and geometrical properties of the gas, sample, and backing material in the cell. For sufficiently high chopping frequency or for a sample with large lateral dimension, the signal is similar to its one‐dimensional counterpart. Departure from one‐dimensional theoretical predictions occurs at chopping frequency for which the lateral dimension is of the order of the thermal diffusional length of the gas. Spot size plays a relatively insignificant role in affecting the signal. These predictions as well as quantitative calculations based on the present theory are in agreement with several recently reported experiments.

ISSN:0021-8979    

DOI:10.1063/1.328255

出版商:AIP    

年代:1980

数据来源: AIP