Fig. 1. Structure diagram of the proposed external-cavity tunable semiconductor laser built in the Littman-Metcalf configuration

Fig. 2. (a) P-I characteristic curve of the free-running half-butterfly (6 pin) packaged semiconductor laser; (b) P-I characteristic curve of external-cavity semiconductor laser with blazed grating (Output wavelength is 1580 nm)

Fig. 3. (a) Relationship between threshold current and lasing wavelength; (b) Output lasing wavelength versus injection current; Inset: lasing wavelength of the proposed external-cavity laser at different injection currents; (c) Tuning range of the proposed external-cavity tunable semiconductor laser with injection current of 410 mA; (d) Output power of the presented external-cavity laser versus lasing wavelength

Fig. 4. Mode-hopping free performance curve of external-cavity semiconductor laser with blazed grating

Fig. 5. (a) Lasing wavelength stability of the proposed external-cavity tunable semiconductor laser; (b) Output optical power stability of the proposed external-cavity tunable semiconductor laser

Fig. 6. Relationship between the output spectral linewidth and the resonant output wavelength