By Marcus Duelk, Mathieu Faucher & Marco Rossetti The rapid evolution of photonics is reshaping what’s possible in precision sensing, quantum technologies, and advanced imaging. At the core of many of these breakthroughs lies a fundamental component: the single-frequency laser. As industries demand higher spectral purity, improved stability, and greater integration, semiconductor laser technologies are being pushed further than ever before. indie has recently showcased two major advancements that illustrate how compact semiconductor platforms can unlock new performance levels across the visible and infrared domains. The first centers on GaN-based DFB lasers that extend high-coherence, single-frequency operation across the 399–521 nm range, offering unprecedented stability, power scaling, and spectral purity in the visible spectrum. The second highlights a new approach to optical coherent sensing, leveraging an ultranarrow-linewidth InP DFB laser co-packaged with silicon photonics to deliver a compact, costeffective coherent transceiver suitable for distributed sensing applications. Pushing the limits of visible single-frequency lasers Single-frequency lasers are essential tools in modern photonics. Their extremely stable and spectrally pure light enables applications ranging from precision spectroscopy and quantum technologies to sensing, metrology, and advanced displays. Recent advances in GaN-based distributed feedback (DFB) laser diodes are opening new possibilities across the visible spectrum. Our latest work demonstrates compact semiconductor lasers operating from 399 nm to 521 nm based on GaN compound semiconductors and having on-chip gratings realized by electron-beam lithography. The lasers deliver: True single-frequency emission with hop-free stable operation over time and temperature Sub-MHz intrinsic linewidth and a ten-fold improvement in relative intensity noise compared to standard Fabry-Perot laser diodes Precise wavelength control via temperature and current that allow for precise tuning to specific atomic or ionic transitions Excellent long-term reliability similar to standard laser diodes of several ten thousand hours of operation Some applications—such as Raman spectroscopy or quantum computing—require higher optical power than a simple DFB laser can provide, while maintaining single-frequency operation. To address this, we realized a DFB-MOPA architecture (Master Oscillator Power Amplifier). By combining a single-frequency DFB laser with an integrated amplifier section on the same chip, we achieved: >200 mW single-frequency output in continuous-wave operation Up to 400 mW in pulsed mode More than 4x power improvement compared to conventional DFB devices Beyond these results, we are continuing to expand our wavelength-agnostic GaN laser platform, extending the accessible range towards shorter wavelengths in the near-UV and towards longer wavelengths in the deep-green. These developments highlight the potential of GaN photonics as a scalable platform for compact, high-power, and spectrally pure visible lasers, supporting next-generation systems in spectroscopy, sensing, quantum technologies, and advanced imaging. indie DFB Laser Engines To see the full presentations : Low-threshold GaN laser diodes with ultra-short gain sections and passive waveguides & GaN-DFB lasers covering the 400–520nm spectrum From FMCW Automotive LiDAR to Optical Coherent Sensing solutions Optical coherent sensing offers highly sensitive and powerful detection capabilities. However, the complexity and cost of coherent sensing systems have traditionally limited their adoption in a broader range of sensing applications. indie Photonics team wanted to demonstrate that these challenges can be mitigated by employing a well-designed narrow-linewidth distributed feedback (DFB) laser co-packaged with a silicon photonics IQ receiver chip and, when required, a semiconductor optical amplifier (SOA). The resulting coherent transceiver is extremely