The effective population inversion of H-2(11/2) from S-4(3/2) state of Er3+ ions can be achieved through the annihilation of phonons; random lasing action from BLF films embedded with Yb3+/Er3+ codoped BLF nanocrystals is demonstrated and high ambient temperature (>433 K) operation lasers with a very low excitation threshold (<530 nJ cm(-2)) are realized.