Upon excitation of a material below its fundamental transition, cooling of the lattice results if the subsequent emission is predominantly radiative. Despite overwhelming experimental success, it remains a challenge to understand the microscopic nature of detrimental processes that can even prevent cooling. We apply ultrafast spectroscopy to resolve the laser refrigeration cycle in the time domain. Strong evidence for lattice cooling on picosecond timescales in bulk GaAs/InGaP double-heterostructures and GaAs/AlGaAs quantum wells establishes the non-local nature of the parasitic mechanisms. Further precision measurements investigating long-time dynamics are currently underway to resolve detrimental heating in bulk GaAs for the first time.
Jan F. Schmidt, Timo Raab, Jannis Oelmann, and Denis V. Seletskiy, "Investigation of the laser cooling cycle in the time domain (Conference Presentation)," Proc. SPIE 10121, Optical and Electronic Cooling of Solids II, 101210G (Presented at SPIE OPTO: February 02, 2017; Published: 20 April 2017); https://doi.org/10.1117/12.2251938.5397967389001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon