High performance planar microcavity organic semiconductor lasers based on thermally evaporated top distributed Bragg reflector

Abstract

High performance organic semiconductor lasers (OSLs), especially those under current injection, have been sought for decades due to their potentially great applications in the fields such as spectroscopy, displays, medical devices, and optical interconnection. The design and fabrication of high-quality resonators is a prerequisite for high performance OSLs. In case of planar microcavities, the fabrication process of top distributed Bragg reflectors (DBRs) usually requires electron beam evaporation or manual lamination on top of organic thin-film layers, which can lead to issues including degradation of the organic materials, large-scale non-uniformity, and difficulties for current-injection. Here, we report a non-destructive way of fabricating a top DBR by thermal evaporation. The top DBR based on thermally evaporated alternative TeO x /LiF stacks show low morphological roughness, high process tolerance, and high reflectivity. Moreover, the deposition process causes negligible damage to the organic thin-film layers underneath. With the combination of a conventional e-beam evaporated bottom DBR, a high performance planar microcavity OSL with a low threshold of 1.7 μJ cm -2 , emission linewidth of 0.24 nm, and angular divergence <3° have been successfully achieved under Nitrogen laser pumping.Similar performance, with a high Gaussian beam quality comparable with that of an ideal diffraction-limited beam, was also obtained under diode pumping, showing the potential of this technique for building compact and cost-effective organic lasers with good beam quality. Our result will open a promising route for future high performance 3 microcavity optoelectronic devices, especially for laser devices under current-injection.

Solid‐State Red Laser with a Single Longitudinal Mode from Carbon Dots

“…However, it is difficult to precisely control the light field and to flexibly select the modes in these resonators [51] . In contrast, the planar microcavity structure is uniform and flat, which can effectively reduce incoherent scattering loss [52] . Its optical feedback direction can also be consistent with the device's light output direction, which helps to enhance the interaction between the light field and the excitons in the light‐emitting layer, thus improving light output efficiency.…”

“…Furthermore, the threshold of CD lasers could be further reduced by improving the quality of the cavities. For instance, more‐precise and non‐destructive preparation methods such as electron beam evaporation [64] and thermal evaporation [52] can further improve the flatness of the device and accurately tune the length of the planar microcavity. Eventually, we envisage that further innovations in heat management strategies such as adopting highly thermally conducting substrate and additives [65] could further reduce the lasing threshold and may enable stable continuous‐wave operation at room temperature.…”

Low Threshold Room Temperature Polariton Lasing from Fluorene‐Based Oligomers

“…As a result of this advance, we achieve for the first time, polariton lasers with pump threshold fluences as low as current state‐of‐the art organic cavity surface‐emitting lasers with similar structures. [ 36–40 ] Our threshold is still slightly higher than of the very best organic distributed feedback (DFB) lasers because of the much longer interaction lengths with the gain material in such lateral structures [ 41 ] and the scope for precise control of feedback and output coupling (such as using substructured gratings [ 42 ] ). The low polariton lasing thresholds in BSFCz and BSTFCz cavities are attributed to the simultaneous manifestation of strong absorption without severe concentration quenching leading to effective strong coupling, negligible exciton‐exciton annihilation [ 26,43 ] of the two materials and increased radiative component of the LPB by negative detuning leading to the effective population of the LPB, and the relatively high quality factor of the two cavities.…”

Solid‐State Red Laser with a Single Longitudinal Mode from Carbon Dots

“…[51] In contrast, the planar microcavity structure is uniform and flat, which can effectively reduce incoherent scattering loss. [52] Its optical feedback direction can also be consistent with the deviceslight output direction, which helps to enhance the interaction between the light field and the excitons in the light-emitting layer, thus improving light output efficiency. More importantly,t he Purcell effect in am icrocavity can also effectively control the radiative transition of the gain material, which can lower the lasing threshold.…”

“…Specifically,weanticipate that full-color fluorescent CDs with both high stability and high PLQYs could be obtained by finetuning the content of graphitic nitrogen, further optimizing the chemical composition and electronic structure of the electron-donating groups,and improving surface passivation. Furthermore,t he threshold of CD lasers could be further reduced by improving the quality of the cavities.For instance, more-precise and non-destructive preparation methods such as electron beam evaporation [64] and thermal evaporation [52] can further improve the flatness of the device and accurately tune the length of the planar microcavity.E ventually,w e envisage that further innovations in heat management strategies such as adopting highly thermally conducting substrate and additives [65] could further reduce the lasing threshold and may enable stable continuous-wave operation at room temperature.…”