  Since the first demonstration of optical refrigeration in a rare-earth-doped
glass nearly 30 years ago, the nascent field of laser cooling solids has
progressed significantly. It is now possible to demonstrate payload cooling to
~91 K using laser-excited ytterbium-doped fluoride crystals. Realizing lower
temperatures, however, requires achieving ultrahigh purities in existing rare
earth-doped crystals or establishing new cooling media. For the latter,
semiconductors are an obvious choice given higher cooling power densities and
predicted cooling floors as low as 10 K. This has stimulated a race to
demonstrate the optical refrigeration of a semiconductor. It is therefore
timely to systematize the necessary and sufficient experimental minimum
criteria for reporting optical refrigeration results to elevate the reliability
and reproducibility of current and future optical refrigeration claims.
  We distill an optical refrigeration Experimental Minimum (EM) that we propose
will standardize the reporting of new cooling results. EM tenets fall into the
following categories: demonstrations of explicit heating vs cooling, optical
cooling metrics, thermodynamic consistency, and reliable temperature
measurements.
  All optical refrigeration claims should demonstrate the above four criteria
to ensure their reliability and verifiability. We further propose that the EM
serve as a guide for reviewing literature claims in the field.
