Taking 'Narrow' to the Limit: Litecore's In-House External-Cavity Narrow-Linewidth Laser Delivers kHz-Class

Coherence

As optical communications and advanced sensing technologies continue to accelerate, linewidth has become one of the key benchmarks of laser performance. Fujian Z.K. Litecore Co., Ltd. ("Litecore") has now introduced its independently developed external-cavity narrow-linewidth laser (ECL). Backed by end-to-end in-house expertise spanning gain-chip materials and external-cavity architecture, the device achieves a typical ultra-narrow linewidth below 3 kHz, an important step forward for domestically developed high-end lasers in coherence control.

Engineering at the Core: An In-House Gain Chip for kHz-Class Coherence

Litecore's independently developed C-band gain chip forms the technical foundation of the product. By mastering the gain spectrum of active-region materials and carrier-dynamics mechanisms, the team can precisely engineer spontaneous-emission behavior. On this basis, Litecore developed a proprietary external-cavity architecture that optically extends one or both facets of a conventional laser gain chip. Multiple round trips in the extended cavity strengthen mode selection, enabling three simultaneous advances: narrower linewidth, higher output power, and stable single-longitudinal-mode operation. Litecore controls the entire gain-chip chain in house—from epitaxial structure and quantum-well materials to waveguide design and process implementation, reducing dependence on external suppliers and foundry capacity.

Figure 1. Frequency spectrum (typical linewidth < 3 kHz)     

Figure 2. Optical spectrum (typical SMSR > 50 dB)

Leading Performance: Ultra-Narrow Linewidth and High Thermal Stability

A narrower linewidth provides higher coherence and lower phase noise. Litecore's external-cavity laser delivers a typical linewidth below 3 kHz. This performance results from precision optical-path design: the photon round-trip path is lengthened within the cavity, physically suppressing phase perturbations caused by spontaneous emission. The result is a narrow-linewidth source that moves beyond basic functionality toward a production-ready, platform-level domestic solution. The device supports wide-temperature operation from -5°C to 65°C. With precision TEC control, wavelength stability is better than ±1 pm, making it suitable for both laboratory instruments and outdoor cabinets despite temperature variation.

Figure 3. Wavelength and Output-Power Stability of the Ultra-Narrow-Linewidth Laser

Comprehensive Specifications: Full C-Band Coverage for Multiple Applications

Litecore's ECL narrow-linewidth laser is offered in an industry-standard 14-pin butterfly (BTF) package compatible with mainstream optical-module interfaces, enabling straightforward integration without additional redesign. It covers the entire C-band from 1530 to 1565 nm and aligns with the ITU-T wavelength grid. Key performance includes a linewidth below 3 kHz, a side-mode suppression ratio (SMSR) above 50 dB, and single-longitudinal-mode output power above 10 dBm. Litecore maintains end-to-end control from chip design and external-cavity packaging through volume manufacturing and delivery. Across quantum computing, coherent communications, LiDAR, fiber-optic sensing, and precision metrology, Litecore provides external-cavity narrow-linewidth lasers with low phase noise and high SMSR.

Narrow-linewidth lasers are the "heart" of optical communications and precision sensing. Litecore is one of the few domestic narrow-linewidth source suppliers with in-house laser-chip R&D capability. By tightly integrating its proprietary gain chip with external-cavity technology, Litecore has built a technology moat at the chip level. Combined with the market opportunity created by supply-chain localization, this approach reduces system vendors' dependence on imported high-end light sources and provides a secure, independently controlled core optical engine for domestic communications and sensing systems advancing toward higher frequencies and longer transmission distances.