tailieunhanh - Advances in optical and photonic devices Part 4

Tham khảo tài liệu 'advances in optical and photonic devices part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A Tunable Semiconductor Lased Based on Etched Slots Suitable for Monolithic Integration 51 Relatively large power variations can be seen mainly because the front mirror current has been changed significantly in the scan in order to fully explore the tuning characteristics of the laser. Fig. 13 shows a diagram of the wavelength peaks and their corresponding SMSRs. A discrete tuning behaviour can be clearly seen over a tuning range of over 30 nm. With this experimental arrangement a total of 13 discrete wavelengths can be accessed with a wavelength spacing around 3 nm as expected for the present design. 11 of the modes have a SMSR larger than 30 dB except the 1st and 8th modes whose SMSR is around 20 dB. Fig. 13. Three section tunable laser SMSR versus wavelength for different mirror section injection currents. The second laser described here is similar to the one described above however no QWI is used and therefore the wavelength is tuned around 1550 nm. Fig. 14 shows a wavelength tuning map versus both mirror section injection currents. Discrete mode hopping occurs at the boundaries of each different color section within this map. A total discontinuous tuning range of more than 40 nm is observed. The SMSR map versus both mirror currents is shown in Fig. 15. Clear islands of stable wavelength and high SMSR are observed in the maps. Fig. 14. Wavelength tuning map versus both mirror section injection currents. 52 Advances in Optical and Photonic Devices The threshold current is difficult to determine accurately as the device has three sections but when both mirror section injection currents are set for a particular mode a threshold current of 56 mA in the gain section is observed. When all three sections are biased together a threshold current of 146 mA is observed. Fig. 15. SMSR tuning map versus both mirror section injection currents. For comparison a four section sample grated distributed Bragg reflector SG-DBR laser wavelength map versus mirror section currents is