We report 20 Gb/s transmission of four-level pulse amplitude modulation (PAM) signal using a directly modulated tunable distributed Bragg reflector (DBR) laser. Transmission distance over 20 km was achieved without using optical amplifiers and optical dispersion compensation modules. A wavelength tuning range of 11.5 nm and a 3 dB bandwidth greater than 10 GHz over the entire wavelength tuning range were obtained.

Heterogeneously integrating III-V materials on silicon photonic integrated circuits has emerged as a promising approach to make advanced laser sources for optical communication and sensing applications. Tunable semiconductor lasers operating in the 2–2.5 μm range are of great interest for industrial and medical applications since many gases (e.g., CO2, CO, CH4) and biomolecules (such as blood glucose) have strong absorption features in this wavelength region. The development of integrated tunable laser sources in this wavelength range enables low-cost and miniature spectroscopic sensors. Here we report heterogeneously integrated widely tunable III-V-on-silicon Vernier lasers using two silicon microring resonators as the wavelength tuning components. The laser has a wavelength tuning range of more than 40 nm near 2.35 μm. By combining two lasers with different distributed Bragg reflectors, a tuning range of more than 70 nm is achieved. Over the whole tuning range, the side-mode suppression ratio is higher than 35 dB. As a proof-of-principle, this III-V-on-silicon Vernier laser is used to measure the absorption lines of CO. The measurement results match very well with the high-resolution transmission molecular absorption (HITRAN) database and indicate that this laser is suitable for broadband spectroscopy.

A band-gap-tailored random laser with a wide tunable range and low threshold through infrared radiation is demonstrated. When fluorescent dyes are doped into the liquid crystal and heavily doped chiral agent system, we demonstrate a wavelength tuning random laser instead of a side-band laser, which is caused by the combined effect of multi-scattering of liquid crystal (LC) and band-gap control. Through rotating the infrared absorbing material on the side of the LC cell, an adjustable range for random lasing of 80 nm by infrared light irradiation was observed.

We experimentally demonstrated a method of generating continuously wavelength-switchable optical vortex beams (OVBs) in an all-fiber laser. A polarization-dependent microknot resonator (MKR) functions as comb filter and accounts for the narrow linewidth (0.018 nm) of multiwavelength channels. The wavelength interval corresponds to the free spectral range of the MKR. We exploit a fused SMF–FMF (single mode fiber–few mode fiber) mode coupler to obtain broadband mode conversion and successfully achieve multiwavelength switchable OVBs. As far as we know, this is the first report about identical multiwavelength vortex beams with topological charges of ±1. It has been verified that each channel of the vortex beams preserves the same orbital angular momentum (OAM) properties through their clear spiral interferograms. Multiwavelength vortex beams with identical OAM properties are desirable for multiplexing, exchanging, and routing to further improve the capacity of optical fiber transmission.

A multi-wavelength sampled Bragg grating (SBG) quantum cascade laser array operating between 7.32 and 7.85 μm is reported. The sampling grating structure, which can be analyzed as a conventional grating multiplied by a sampling function, is fabricated by holographic exposure combined with optical photolithography. The sampling grating period was varied from 8 to 32 μm, and different sampling order ( 1st, 2nd, and 3rd order) modes were achieved. We propose that higher-order modes with optimized duty cycles can be used to take full advantage of the gain curve and improve the wavelength coverage of the SBG array, which will be beneficial to many applications.

In this work, we investigate the methods to improve the performance of the swept source at 1.0 μm based on a polygon scanner, including in-cavity parameters and booster structures out of the cavity. The three in-cavity parameters are the cavity length, the rotating speed of the polygon scanner, and the in-cavity energy. With the decrease of cavity length, the spectrum bandwidth becomes wider and the duty cycle becomes higher. With the increase of the rotating speed of the polygon, the spectrum bandwidth becomes narrower, and the duty cycle becomes lower but the repetition rate becomes higher. With more energy in-cavity, the spectrum bandwidth becomes wider and the duty cycle becomes higher. The booster structures include the buffered structure, secondary amplifier, and dual-semiconductor optical amplifier configuration, which are used to increase the sweep frequency to 86 kHz, the output power to 18 mW, and the tuning bandwidth to 131 nm, respectively.

The laser performance of a new Yb:germanophosphate (Yb:GP) glass is investigated. A maximum output power of 826 mW at 1063 nm is achieved with direct diode pumping at 976 nm. The wavelength is tuned from 1034.47 to 1070.83 nm, corresponding to a tuning range of 36.36 nm. Thermal lens effects are investigated to optimize the optical cavity.

A wavelength-swept laser is constructed using a free space external cavity configuration coupled with a fiber-based ring cavity at the 850 nm region. The external cavity filter employs a galvo-mirror scanner with a diffraction grating for wavelength selection. The filter is connected to a ring cavity through an optical circulator. The ring cavity contains a broadband semiconductor optical amplifier with a high optical output. The performance of this laser is demonstrated with broad bandwidths and narrow linewidths. The 3 dB linewidth and the bandwidth of this source are 0.05 nm (～20 GHz) and 48 nm, respectively. The maximum output power is 26 mW at 160 mA current.

In this Letter, a simple and passively mode-locking Yb-doped all fiber laser using a nonlinear polarization rotation technique operating under dissipative soliton (DS) or dissipative soliton resonance (DSR) conditions is proposed. Furthermore, using a combination of a bandpass filter and a Loyt filter, tunable single-wavelength or dual-wavelength operation under two different conditions is realized, respectively. The tunable single-wavelength DS laser has a 5 nm tuning range from 1029 to 1034 nm with a pulse width of 110 ps. The tunable single-wavelength DSR operation laser has a range of 4 nm. In-depth research on the mechanism of the conversion between DS and DSR is carried out. Particularly, under dual-wavelength DSR operation, the obtained step-like pulses consist of two rectangular pulses with different energies. This work could help give a deeper insight into normal dispersion pulses.

We report a simple and compact all-fiber laser system that is capable of generating widely tunable femtosecond pulses from 1.6 to 2.32 μm. The pulses are produced by utilizing the soliton self-frequency shift in a highly nonlinear fiber pumped by an Er-doped mode-locked fiber laser. Two stages of single-clad Tm:fiber amplifiers are used to amplify the pulses to a higher pulse energy of 10.9 nJ with pulse width of 94 fs, and corresponding to peak power of 105 kW at around 1.93 μm. Running a few hours, the all-fiber laser system exhibits exceptional stability with a signal-to-noise ratio as high as 70 dB.