Photonic crystal lasers promise improved performance in applications such as telecommunications. To better understand their behavior, a team of researchers at the University of Southern California in Los Angeles has investigated the effects of local and substrate temperature on the performance of photonic crystal lasers operating at room temperature.The scientists, who reported their findings in the Oct. 28 issue of Applied Physics Letters, constructed a sample laser using four compressively strained InGaAsP quantum wells in a 224-nm-thick semiconductor membrane. The absence of 19 airholes in the triangular lattice etched into the structure formed the resonator cavity. A 100X microscope objective focused 865-nm radiation from the vertical-cavity surface-emitting laser excitation source onto the sample.Simulations of thermal effects on the photonic crystal laser suggested that optical pumping would heat the defect region by up to 112 K. The calculation was supported by the observation of a redshift in the lasing wavelength of the sample under test from the 1550-nm spontaneous emission spectrum of the unpatterned material. Heating the structure through its substrate to 293, 308 and 323 K also increased the threshold input power.