# Multiscale Fabrication Process Optimization of DFB Cavities for Organic Laser Diodes

## TL;DR

This paper describes optimizing the fabrication of micro-cavities for organic laser diodes to enable efficient light emission and high current operation.

## Contribution

The study introduces a multiscale fabrication process for DFB micro-cavities integrated with OLEDs for organic laser diodes.

## Key findings

- DFB micro-cavities were fabricated with nanometer-scale precision using e-beam lithography.
- The device achieved a peak current density of 14 kA/cm2 without compromising electrical operability.
- Optimal fabrication conditions included specific resist thickness, dose, and development time.

## Abstract

In the context of the quest for the Organic Laser Diode, we present the multiscale fabrication process optimization of mixed-order distributed-feedback micro-cavities integrated in nanosecond-short electrical pulse-ready organic light-emitting diodes (OLEDs). We combine ultra-short pulsed electrical excitation and laser micro-cavities. This requires the integration of a highly resolved DFB micro-cavity with an OLED stack and with microwave electrodes. In a second challenge, we tune the cavity resonance precisely to the electroluminescence peak of the organic laser gain medium. This requires precise micro-cavity fabrication performed using e-beam lithography to pattern gratings with a precision in the nanometer scale. Optimal DFB micro-cavities are obtained with 300 nm thick hydrogen silsesquioxane negative-tone e-beam resist on 50 nm thin indium tin oxide anode exposed with a charge quantity per area (i.e., dose) of 620 µC/cm2, developed over 40 min in tetramethylammonium hydroxide diluted in water. We show that the integration of the DFB micro-cavity does not hinder the pulsed electrical operability of the device, which exhibits a peak current density as high as 14 kA/cm2.