Wavelength-tunable passively mode-locked all-fiber laser at 1.5 μm

All-polarization-maintaining, efficiently wavelength-tunable, Er-doped mode-locked fiber laser with a compact reflective Lyot filter

Wavelength tunable mode-locked fiber lasers have highly potential applications in precision spectroscopy, nonlinear microscopy and photonic sensing. Here, we present a compact and thermal-sensitive reflective Lyot filter and utilize it for all-polarization-maintaining efficiently wavelength-tunable Er-doped carbon-nanotube-mode-locked laser for the first time, to the best of our knowledge. The output wavelength of the laser can be tuned from 1544.46 nm to 1572.71 nm, with a wide tuning range of 28.25 nm, and a remarkable tuning efficiency of 0.589 nm/°C, when the angle-spliced fiber is only 8.2 cm and the free spectral range of the filter is 31.32 nm. Dual-wavelength mode-locking is also achieved at boundary temperatures when increasing the pump power. Due to its compact size and reflection configuration, the proposed reflective Lyot filter is promising for realizing highly efficient wavelength tuning and multiwavelength generation in all-polarization-maintaining fiber lasers where reflective filters are needed.

Full C-band wavelength-tunable, 250 MHz repetition rate mode-locked polarization-maintaining fiber laser

We demonstrate a full C-band wavelength-tunable mode-locked fiber laser with a repetition rate of 250 MHz, representing the highest repetition rate for C-band tunable mode-locked lasers thus far to the best of our knowledge. The polarization-maintaining fiber-based Fabry-Perot cavity enables a fundamental repetition rate of 250 MHz with a semiconductor saturable absorber mirror as a mode-locker. We observed a stable and single soliton mode-locking state with wide tunability of the center wavelength from 1505 to 1561 nm by adjusting the incident angle of a bandpass filter inside the cavity. The wavelength-tunable high-repetition-rate mode-locked laser covering the full C-band is expected to be a compelling source for many frequency-comb-based applications, including high-precision optical metrology, broadband absorption spectroscopy, and broadband optical frequency synthesizers.

Upconversion nanoparticles extending the spectral sensitivity of silicon photodetectors to λ = 1.5 μm

The telecommunication wavelength of λ = 1.5 μm has been playing an important role in various fields. In particular, performing photodetection at this wavelength is challenging, demanding more performance stability and lower manufacturing cost. In this work, upconversion nanoparticle (UCNP)/Si hybrid photodetectors (hybrid PDs) are presented, made by integrating solution-processed Er³⁺-doped NaYF₄ upconversion nanoparticles (UCNPs) onto a silicon photodetector. After optimization, we demonstrated that a layer of UCNPs can well lead to an effective spectral sensitivity extension without sacrificing the photodetection performance of the Si photodetector in the visible and near-infrared (near-IR) spectrum. Under λ = 1.5 μm illumination, the hybrid UCNPs/Si-PD exhibits a room-temperature detectivity of 6.15 × 10¹² Jones and a response speed of 0.4 ms. These UCNPs/Si-PDs represent a promising hybrid strategy in the quest for low-cost and broadband photodetection that is sensitive in the spectrum from visible light down to the short-wave infrared.

Tunable mode-locked erbium-doped fiber laser based on a digital micro-mirror device

A tunable mode-locked erbium-doped fiber laser with a digital micro-mirror device (DMD) as the wavelength tuner and nonlinear amplifying loop mirror as the mode-locked device is proposed and experimentally demonstrated. The mode-locked pulse with the center wavelength of 1538-1565 nm continuously tunable is achieved. The average power of the output pulse is 1.028 mW, the pulse repetition frequency is 1.7 MHz, the pulse duration is 616 fs, and the single pulse energy is 0.6 nJ. By controlling the DMD, the center wavelength can be fine-tuned with the tuning accuracy of 0.07 nm. With the increase of the pump power, the traditional soliton pulse is transformed into a noise-like pulse (NLP), and the power of the NLP can reach 34 mW. This mode-locked process can work for a long time and is almost unaffected by the external environment. These results are very useful for applications where pulsed lasers with different wavelengths are needed.