Lasers and Quantum Electronics

Lasers operate by converting a population‐inverted gain medium into a coherent light source via stimulated emission within an optical resonator. Quantum electronics advances have enabled the tailoring of light–matter interactions in micro- and nanostructures—quantum wells, wires and dots—to enhance gain, reduce threshold and control noise. Semiconductor lasers benefit from direct bandgap materials and heterostructure engineering, achieving compact, efficient sources spanning near-infrared to mid-infrared. Concurrently, integrated photonics leverages high-quality-factor microresonators and waveguide platforms to realise ultranarrow linewidths, low-noise oscillators and chip-scale frequency combs. Emerging architectures—distributed feedback, vertical-cavity surface-emitting lasers, quantum-cascade and interband-cascade designs—provide versatile platforms for optical communication, sensing, spectroscopy and quantum information. Central themes include mastering population inversion, minimising spontaneous emission noise, controlling optical feedback dynamics and maximising the quality factor of resonant cavities.

Research from Nature Portfolio

A planar integrated all-waveguide silicon-nitride resonator has reached an intrinsic quality factor of over 400 million, yielding sub-megahertz linewidth in a compact chip-scale platform. By rigorous suppression of scattering and absorption losses, the device achieves 453 kHz intrinsic linewidth, enabling stable narrow-linewidth lasing suited to coherent communications and frequency references.

Broadband cavity-enhanced photothermal spectroscopy has been employed to measure the material-limited quality factors and Kerr nonlinearities of key photonic materials (SiO₂, Si₃N₄, Al₀.₂Ga₀.₈As, Ta₂O₅). By correlating photothermal responses with resonance linewidths, the work establishes fundamental limits on optical losses and guides material choice for next-generation high-coherence microresonators.

Research from all publishers

A multijunction cascaded vertical-cavity surface-emitting laser has achieved a record power-conversion efficiency of 74 % under nanosecond pulsed drive. By stacking fifteen active junctions in series, the design surpasses edge-emitting lasers in differential quantum efficiency and demonstrates the potential of cascaded architectures for high-efficiency, high-brightness light sources.

A single-mode vertical-cavity surface-emitting laser incorporating a chirped high-contrast metastructure top mirror has enabled 106 Gbps PAM4 transmission over single-mode fiber. The spatially graded reflectivity mirror suppresses higher-order modes, delivering over 40 dB side-mode suppression and an open eye diagram at 106 Gbps, pointing the way to ultrahigh-speed optical interconnects.

High-power, low-relative-intensity-noise single-mode distributed-feedback laser diodes with 8 µm ridges have been demonstrated for optical communications. These devices deliver over 170 mW of single-mode output, RIN below –157 dB/Hz and SMSR above 55 dB, while supporting 8.6 nm of thermal tuning, meeting stringent requirements for high-capacity WDM systems.

Lasers and Quantum Electronics publication trend

The graph below shows the total number of articles in lasers and quantum electronics across all publications each year (not limited to Nature Index journals).

Technical terms

Stimulated emission: Process by which an incident photon induces an excited electron to decay, emitting a second photon of identical phase, frequency and direction.

Population inversion: Condition in which more electrons occupy an excited state than the lower state, enabling net optical gain via stimulated emission.

Optical cavity: Resonant structure, usually defined by mirrors or distributed feedback, that traps light to build up coherent oscillation.

Quality factor (Q): Dimensionless parameter measuring the energy storage-to-loss ratio of a resonator; higher Q indicates narrower resonance linewidth.

Linewidth: Spectral width of laser emission; inversely proportional to coherence time and limited by quantum and technical noise.

Cavity mode: Discrete resonant frequency of an optical cavity, determined by its geometry and refractive index distribution.

References

1. 422 Million intrinsic quality factor planar integrated all-waveguide resonator with sub-MHz linewidth. Nature Communications (2021).
2. Probing material absorption and optical nonlinearity of integrated photonic materials. Nature Communications (2022).
3. Multi-junction cascaded vertical-cavity surface-emitting laser with a high power conversion efficiency of 74%. Light: Science & Applications (2024).
4. Single-mode chirped high-contrast metastructure VCSEL for 106 Gbps PAM4 transmission. Optica (2024).
5. Wide-waveguide high-power low-RIN single-mode distributed feedback laser diodes for optical communication.. Optics Express (2022).
6. Lasers.