In this paper, a widely tunable external cavity diode laser (ECDL) with an ultra-high side mode suppression ratio (SMSR) was fabricated. Three configurations were constructed to investigate the relationship between the grating features and the SMSR. When a 1200 grooves/mm grating with a first order diffraction efficiency of 91% is utilized in the external-cavity laser system, a maximum SMSR of 65 dB can be achieved. In addition, the tunable range reaches 209.9 nm. The results show that the laser performance can be improved by proper high grating groove number and first-order diffraction efficiency.

A narrow linewidth tunable laser source is a critical component in various fields, including laser radar, quantum information, coherent communication, and precise measurement. Tunable external cavity diode lasers (ECDLs) demonstrate excellent performance, such as narrow linewidth, wide tunable range, and low threshold current, making them increasingly versatile and widely applicable. This article provides an overview of the fundamental structures and recent advancements in external cavity semiconductor lasers. In particular, we discuss external cavity semiconductor lasers based on quantum well and quantum dot gain chips. The structure of the gain chip significantly influences laser’s performance. External cavity quantum well laser has a narrower linewidth, higher power, and better mode stability. Conversely, external cavity quantum dot laser provides a wider tunable range and a remarkably lower threshold current. Furthermore, dual-wavelength external cavity tunable diode lasers are gaining importance in applications such as optical switching and terahertz radiation generation. With the continuous optimization of chips and external cavity structures, external cavity diode lasers are increasingly recognized as promising light sources with narrow linewidth and wide tunability, opening up broader application prospects.

We design a unique external cavity configuration and present an ultra-narrow linewidth external cavity diode laser (ECDL) employing a wide interference filter and diffraction grating. The interference filter is for suppressing the noise floor, and diffraction grating is used for the mode selection. The combination of the filter and diffraction grating can effectively use a narrow linewidth without a significant reduction in optical gain. The Lorentz linewidth reaches 13.6 kHz at a wavelength of 1555 nm. The ECDL can be tuned by rotating the diffraction grating, and a wide tunable range of 40 nm is achieved with a maximum output power of 25.6 mW at an injection current of 200 mA. In addition, the ECDL shows an excellent side mode suppression ratio (SMSR) performance with a maximum of 57 dB at 1555 nm. Additionally, the SMSR changes gently throughout the tuning range at the injection current of 200 mA.

In this paper, a tunable external cavity diode laser (ECDL) based on the first excited states of two independent quantum dot (QD) ensemble has been demonstrated. The device exhibits stabilized lasing with high-power of 120 mW. We attribute the excellent output characteristics of the QD ECDL to carrier radiation recombination in high energy states, which has higher degeneracy than low energy states and can accommodate more carriers. The linewidth of ECDL is less than 0.2 nm, which is also much narrower than most of QD ECDLs as reported. Preliminary discussion attributes the spectra feature to the lower QD density and independent carrier transitions. The tunable range is 28.9 nm (970.1–999 nm) and the wavelength shift with the injection current is 0.7 nm A ⁻¹ .

Electrochemical water splitting is a core component of clean and renewable energy technologies. Developing low-cost, highly active electrocatalysts is critical to enabling its large-scale deployment. Interfacial effects, which govern charge-transfer kinetics and the adsorption of reaction intermediates, play a decisive role in enhancing the activity and stability of water-splitting electrocatalysts. To clarify how interfacial effects regulate catalytic performance, this review summarizes the fundamental principles of interface engineering and recent advances in water-splitting electrocatalysis. In particular, it focuses on how interfacial structures tune the electronic structure of active sites and the adsorption behavior of intermediates through lattice strain, interfacial charge redistribution, and orbital hybridization. These mechanisms collectively enhance the performance of the hydrogen evolution reaction and oxygen evolution reaction. Finally, the review discusses the core challenges facing interface-engineered electrocatalysts for practical water electrolysis and outlines future research directions.