Optically pumped lasing in single crystals of organometal halide perovskites prepared by cast-capping method

Abstract

A simple “cast-capping” method is adopted to prepare single-crystal perovskites of methyl ammonium lead bromide (CH3NH3PbBr3). By capping a CH3NH3PbBr3 solution casted on one substrate with another substrate such as glass, mica, and distributed Bragg reflector (DBR), the slow evaporation of solvent enables large-size cubic crystals to grow between the two substrates. Under optical pumping, edge-emitting lasing is observed based on Fabry–Pérot resonation between parallel side facets of a strip-shaped crystal typically with a lateral cavity length of a few tens of μm. On the other hand, vertical-cavity surface-emitting lasing (VCSEL) is obtained from a planar crystal grown between two DBRs with a cavity thickness of a few μm. Simultaneous detection of those edge- and surface-emissions reveals that the threshold excitation fluence of VCSEL is higher than that of the edge-emitting lasing due to thickness gradient in the planar crystal.

Continuous-wave optically pumped green perovskite vertical-cavity surface-emitter

“…These approaches used hybrid perovskites in the form of powders with vertical cavities [10], cavity-free thin films [11,12], crystals with vertical cavities [13], microdisks/plates with whispering gallery modes (WGMs) [14,15], micro/nanowires with Fabry-Perot (FP) cavities [16,17] and gratings [18], micro/ nanorods with FP cavities [19], cavity-free colloidal quantum dots [20] and WGMs [21], colloidal nanocrystals with WGMs [22], FP cavities [23], and vertical cavities [24]. Compared to ASE, SE typically has a narrower linewidth and obvious threshold, and exhibits beam divergence and polarization [25].…”

“…Compared to ASE, SE typically has a narrower linewidth and obvious threshold, and exhibits beam divergence and polarization [25]. Concerning vertical-cavity approaches, only a few green devices using perovskite powders, crystals, and nanocrystals were reported for ASE [10,13] and SE [24] regimes. However, thick perovskite active layers were used without any optical waveguiding heterostructures and, thus, no cavity resonances were properly obtained.…”

“…However, thick perovskite active layers were used without any optical waveguiding heterostructures and, thus, no cavity resonances were properly obtained. Moreover, the formation of the cavities by cast-capping (i.e., casting a perovskite solution on a DBR substrate and then capping it with another DBR and leaving it to dry for bonding) [10,13,24] is neither uniform nor scalable, which led to high operating thresholds and emission wavelength fluctuations [13].…”

“…All perovskites green-light emitters mentioned above [10,11,[13][14][15][16][17][18][19][20][21][22][23][24] were optically pumped using ultrashort pulses (typically, femtoseconds). An optically pumped NIR perovskite laser using longer pulses (nanoseconds) was recently demonstrated [26], but it was operated in a cryogenic environment.…”

“…The use of PMMA in the heterostructured active region also reduced the ASE threshold by half [12] due to the smoother surface, surface passivation, and waveguiding effects. Furthermore, by heterostructure engineering, only a nanoscale perovskite layer is required (∼82 nm) for our device compared to the larger thickness of microscales required for other devices [10,13,24]. A thin perovskite layer is essential to form heterostructures and to reduce material defects and thermal resistance [34].…”