Effect of the Cavity Resonance-Gain Offset on the Output Power Characteristics of GaSb-Based VECSELs

Optically pumped VECSELs: review of technology and progress

“…These effects can lead to excessive heating with increasing pump power, which then reduces the emission efficiency even further via increased non-radiative recombination and carrier leakage. The VECSEL heating also red-shifts the emission wavelength, which can lead to a mismatch between the emission wavelength and the resonant periodic gain structure [35,36]. Consequently, the output power of a VECSEL exhibits a thermal roll-over with increased pump power.…”

“…This is particularly true for resonant gain mirrors that require an optimized detuning between resonance and photoluminescence peak wavelengths [36,149]. The detuning should eventually be zero at the targeted operation temperature and pump power.…”

Semiconductor disk lasers (VECSELs)

“…With respect to the latter, each SDL gain structure has an optimum temperature at which the gain and the resonances overlap such that the effective gain is optimised, beyond which thermal rollover will eventually shut off the laser. However, while this overlap can be partly accounted for by designing in an appropriate offset for the cold laser, 37 for example, the room temperature RPG wavelength may be fi xed at a longer wavelength than the peak of the quantum well gain (which has higher d λ /d T ), thermal escape of the carriers from the quantum wells limits high temperature operation. The pump induced temperature increase, therefore, ultimately limits the maximum output power of an SDL.…”

GaSb-based VECSEL exhibiting multiple-watt output power and high beam quality at a lasing wavelength of 2.25 μm

“…Taking into account the different temperature-tuning rates of the gain spectrum and the microcavity resonance, the gain peak offset with respect to the microcavity resonance could be calculated at room temperature. It has been shown that the gain peak offset at room temperature is a key parameter for the design of high performance VECSELs [13]. For the present VECSEL structures the MQW active region was grown such as to provide a gain peak which is blueshifted with respect to the spectral position of the cavity resonance (see Fig.…”