Figure 4

Spectra, power, and temperature characteristics. (a) Emission spectra from QDCL recorded at room temperature for different drive currents with a pulsed width of 1 μs and repetition frequency of 50 kHz. (b) Typical lasing spectrum from the QDCL recorded at 81 K with a pulsed width of 2 μs and repetition frequency of 1.5 kHz. The inset shows the voltage-current power curves. (c) Light-current (L-I) characteristics of QDCL operated in pulsed mode with a pulsed width of 2 μs and repetition frequency of 5 kHz. (d) Threshold current as a function of heat sink temperature in pulsed operation for another typical laser device. The solid curve represents fit using the empirical exponential function, I_th = I₀ exp(T / T₀).