tailieunhanh - Advances in Optical and Photonic Devices 2011 Part 2

Tham khảo tài liệu 'advances in optical and photonic devices 2011 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 16 Advances in Optical and Photonic Devices comparable to the To range 50-70 K of the equivalent QW structure. In Fig. 12 b only a distinctive ground state lasing with the wavelength coverage of 15 nm is observed below injection of x Jth. This broad lasing linewidth again suggests collective lasing actions from Qdashes with different geometries. In addition the quasi-supercontinuum lasing spectrum at high current injection 4 x Jth without distinctive gain modulation Harris et al. 1997 further validates the postulation of uniform distribution of dash electronic states in a highly inhomogeneous active medium. At J x Jth the bistate lasing is evident. The simultaneous lasing from both transition states Hadass et al. 2004 is attributed to the relatively slow carrier relaxation rate and population saturation in the ground state in lowdimensional quantum heterostructures. The bistate lasing spectrum is progressively broadened with increasing carrier injection up to a wavelength coverage of 85 nm at J 4 x Jth which is larger than that of the as-grown laser 76 nm as shown in Fig. 11 and Fig. 13. A center wavelength shift of 100 nm and an enhancement of the broadband linewidth which is attributed to the different interdiffusion rates on the large height distribution of noninteracting Qdashes at an intermediate intermixing are achieved after the intermixing. The inset of Fig. 13 showing the changes of FWHM of the broadband laser with injection depicts that energy-state-hopping and multi-state lasing emission from Qdashes with Fig. 13. The wavelength tune quasi-supercontinuum quantum dash laser from pm to pm center wavelength. The lasing coverage increases from 76 nm to 85 nm after intermixing process. The inset shows the FWHM of the broadband laser in accordance to injection above threshold up to J 4 x Jth. Fig. 14. a Spaced and quantized energy states from ideal Qdot samples. b Large broadening of each individual quantized energy state contributes to laser