optical gain in semiconductor laser

... 2004 Marcel Dekker, Inc. 3 StimulatedEmissionandOptical GaininSemiconductors Thischapterpresentsthebasictheoryandcharacteristicsofstimulated emissionandopticalamplificationgaininsemiconductors.Theformeristhe mostimportantprinciplethatenablessemiconductorlaserstobeimplemented, andthelatteristhemostimportantparameterforanalysisofthelaser performances.First,stimulatedemissioninsemiconductorsisexplained,and thenquantumtheoryanalysisandstatisticanalysisusingthedensitymatrix oftheopticalamplificationgainaregiven.Stimulatedemissionandoptical gaininsemiconductorquantumwellstructureswillbepresentedinthenext chapter. 3.1BANDSTRUCTUREOFSEMICONDUCTORSAND STIMULATEDEMISSION 3.1.1BandStructureofDirect-TransitionBandgap Semiconductors Semiconductorlasersutilizetheinterbandopticaltransitionsofcarriersina semiconductorhavingadirect-transitionbandgap.Asiswellknowninthe electrontheoryofsolids[1],thewavefunctionofanelectronofwavevector k(momentumhh k )inanidealsemiconductorcrystalcanbewrittenasa Blochfunction j ... 3 StimulatedEmissionandOptical GaininSemiconductors Thischapterpresentsthebasictheoryandcharacteristicsofstimulated emissionandopticalamplificationgaininsemiconductors.Theformeristhe mostimportantprinciplethatenablessemiconductorlaserstobeimplemented, andthelatteristhemostimportantparameterforanalysisofthelaser performances.First,stimulatedemissioninsemiconductorsisexplained,and thenquantumtheoryanalysisandstatisticanalysisusingthedensitymatrix oftheopticalamplificationgainaregiven.Stimulatedemissionandoptical gaininsemiconductorquantumwellstructureswillbepresentedinthenext chapter. 3.1BANDSTRUCTUREOFSEMICONDUCTORSAND STIMULATEDEMISSION 3.1.1BandStructureofDirect-TransitionBandgap Semiconductors Semiconductorlasersutilizetheinterbandopticaltransitionsofcarriersina semiconductorhavingadirect-transitionbandgap.Asiswellknowninthe electrontheoryofsolids[1],thewavefunctionofanelectronofwavevector k(momentumhh k )inanidealsemiconductorcrystalcanbewrittenasa Blochfunction j ... in inversion occupation probability difference f 2 À f 1 and gain spectrum g(hh!) with increasing carrier injection. Stimulated Emission and Optical Gain 45 Copyright â 2004 Marcel Dekker, Inc. ...

... tục in. CHƯƠNG 1: THÔNG TIN VỀ SẢN PHẨM 1.1. ĐẶC TÍNH KỸ THUẬT CỦA MÁY IN Bảng 1.1. Đặc tính kỹ thuật của máy in Đặc tính kỹ thuật Miêu tả Tốc độ in 4 trang trên phút (đối vói máy in HP LaserJet ... đó in lại (xem chương 3, “các thiết lập máy in PCL”. 6. Nếu thay đổi chế độ Auto Continue (tự động tiếp tục) có bật PJL, máy in sẽ tiếp tục in sau 10 giây. 7. Nếu thay đổi chế độ Auto Continue ... vào máy in. Lắp lại nắp che khe cắm bộ nhớ mở rộng, dựng máy in thẳng lên, và cấp nguồn cho máy in. In một bản in kiểm tra (xem chương 3) để kiểm tra xem bộ nhớ đã được thêm vào máy in của...

... choosing the coupling point in the half taper i.e. adjusting the distance from tip to acceptance point we may also find the appropriate position to select one lasing mode. a) b) Fig. 3. Selecting ... Estimating the micro- sphere diameter through peaks distance in these spectrums gave result well matched the one received by optical method. When increasing the pump intensity we obtained laser ... b) Fig. 3. Selecting a single laser mode by changing the acceptance angle: a) three lines emission, marker at 1534.4 nm b) single line at 1534.4 nm. Fig. 4. The wavelength shift in laser spectrum, microsphere...

... low-dimensional semiconductor. 5. Conclusions In this paper, we obtain analytic expression of the parametric transformation coefficient of acoustic and optical phonons in doped superlattices in presence ... combination frequency q l υ ±Ω r (l=1,2,3,4…) will appear. If among the CDW there exits a certain wave having a frequency which coincides, or approximately coincides, with the frequency of optical ... received in revised form 15 August 2009 Abstract. The parametric transformation of acoustic and optical phonons in doped superlattices is theoretically studied by using a set of quantum kinetic...

... low doses of norepinephrine exerted a significant inhibition on lipoysis (Fig. 1C). The initial step involved in the epinephrine ⁄ nor- epinephrine-induced lipolytic cascade includes activa- tion ... lgặkg )1 epinephrine (d) or saline (s), or (B) 0.5 mgặkg )1 B[a]P for the indicated times prior to receiving injections of either saline or 0.25 mgặkg )1 epinephrine. Forty-ve minutes after injection ... differences in FFA concentrations between epinephrine and saline incubations (A). (B) Effect of 15 min preincubation of human adipocytes with either B[a]P (j) or saline (h) followed by 45 min incubation...

... the FEMTOSECOND LASER PROCESSING OF METAL 223 Downloaded By: [Ingenta Content Distribution] At: 19:07 13 December 2007 Similar delays in the beginning of melting were observed during experiments on aluminum ... Thermal Lagging in Ultrafast Laser Heating, Int. J. Heat Mass Transfer, vol. 44, pp. 1725–1734, 2001. 10. L S. Kuo and T. Q. Qiu, Microscale Energy Transfer during Picosecond Laser Melting of Metal ... superheating and that a distinct melt phase develops with duration of the order of nanoseconds. INTRODUCTION In the last few years, the use of femtosecond lasers in materials processing and related...

... phenomena in picosecond laser material interaction Xinwei Wang a, * , Xianfan Xu b a Department of Mechanical Engineering, N104 Walter Scott Engineering Center, The University of Nebraska at Lincoln, Lincoln, ... pulsed laser materials interaction has attracted considerable attention owing to the rapid development of short pulsed lasers and their potential applications in laser- material processing. In this ... revealing the mecha- nism behind the thermal and thermomechanical phe- nomena in ultrafast laser materials interaction. In the past several years, many MD simulations of laser materials interaction...

... fluence in the medium fluence region, i.e., extinction of the laser beam in the plume does not vary with the laser intensity in the medium fluence region. Extinction of the laser beam is determined ... the boiling point wx 5 . The superheating process is represented by the ‘superheating’ line in Fig. 1. However, there is a well defined upper limit for superheating of a liquid, Ž. the spinode ... heating process of a liquid metal by a pulsed laser beam, the phase diagram in the neighborhood of the critical temperature is shown in wx Fig. 1 4 . The ‘normal heating’ line indicates the heating...

... Thermal Lagging in Ultrafast Laser Heating, Int. J. Heat Mass Transfer, vol. 44, pp. 1725–1734, 2001. 10. L S. Kuo and T. Q. Qiu, Microscale Energy Transfer during Picosecond Laser Melting of Metal ... numerically to predict heating, melting, and evaporation of metal under femtosecond laser irradiation. Kinetic relations at the phase-change interfaces are included in the model. The numerical ... found in the literature [1]. This interest has been sparked by the fact that ultrashort lasers offer considerable advantages in machining applications, chief among which are the abilities to machine...

... lag in nanosecond laser ablation Xianfan Xu * School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-1288, USA Abstract This work investigates interface kinetics during ... beam through the laser- induced vapor plume, scattering of laser beam from the laser- induced vapor plume, tran- sient location and velocity of the laser- induced vapor front, and ablation depth per laser ... including pulsed laser deposition and micromachining. Phase explosion induced by laser heating will be briefly described. The nucleation process and its time lag in a superheated liquid leading to phase...

... IV–VI semiconductors has been studied taking PbTe as an example. The stressed semiconductors are being investigated for strained silicon transis- tors, quantum cascade lasers, semiconductor strain ... been investigated [158–165]. These studies revealed some of the interesting features that had been seen in bulk PbTe, such as Fermi level pinning in the case of superconductivity [166]. In Sect. ... Tellurium (Te) has been used as the semiconductor layer in thin- film transistors (TFT) [171], which is being used in CO 2 laser detectors [172], electronic imaging, strain-sensitive devices [173,174],...

... red shift, and FWHM in Raman line-shape increase by the increasing excitation laser power density. Changes in the Raman line-shape are reversible in nature on decreasing the laser power density. This ... heating. Increase in the asymmetry on increasing excitation laser power density is due to Fano interaction between electronic Raman scattering involving photo-excited electrons within elec- tronic ... of phonons in the Si NSs. Many others [3, 4] have explained the asymmetry and downshift in the Raman line-shape in terms of a com- bined effect of quantum confinement and laser heating. Magidson...