Narrow Linewidth External-cavity Laser Research Articles

Dual-module combination with littman crosstalk external cavity for narrow-linewidth blue diode laser

The dense spectral beam combination is vital for achieving high power and brightness output in diode lasers. High-power narrow-linewidth laser modules have been widely studied as the fundamental units. This study presents a dual-module shared external cavity linewidth compression structure with a transmission diffraction grating. With a driving current of 2.4 A and a cooling temperature of 20 °C, the blue diode laser’s external cavity achieved an output power of 49.8 W, a spectral linewidth of 0.321 nm, and a tuning range of 0.817 nm, with an external cavity spectrum locked efficiency of approximately 80.6 %. Additionally, it is observed that crosstalk has a significant influence on the linewidth of the two modules. When one module current locked at 2.4 A and the other increased from 0 A to 2.4 A, the linewidth was reduced from 0.377 nm to 0.321 nm, and linewidth locking was implemented over an output power range from 27 W to 49.8 W. This work reports the highest output power for a blue diode narrow-linewidth external cavity laser.

Narrow Linewidth External Cavity Laser Capable of High Repetition Frequency Tuning for FMCW LiDAR

A light source with well-rounded performance including the narrow linewidth, wide frequency tuning range, high repetition rate and good linearity, is highly sought-after for frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR). In this work, we report a directly frequency modulated external cavity laser with the linewidth of 5.06 kHz. The frequency tuning range of 1.1 GHz, 445.5 MHz, 228.9 MHz are demonstrated at the repetition rate of 1 kHz, 10 kHz and 100 kHz, respectively. The frequency sweep linearization is achieved by iterative learning pre-distortion. The ranging performance with the repetition rate up to 100 kHz is investigated. The signal-to-noise ratio is still higher than 35 dB while the length of delay fiber is 156 m, corresponding to a target 110 m away in free space. These results indicate that the proposed swept-frequency laser has great potential for autonomous driving applications.

Higher-order QAM data transmission using a high-coherence hybrid Si/III-V semiconductor laser.

We experimentally demonstrate the use of a high-coherence hybrid silicon (Si)/III-V semiconductor laser as the light source for a transmitter generating 20 Gbaud 16- and 64- quadrature amplitude modulated (QAM) data signals over an 80 km single-mode fiber (SMF) link. The hybrid Si/III-V laser has a measured Schawlow-Townes linewidth of ${\sim}{10}\;{\rm kHz}$∼10kHz, which is achieved by storing modal optical energy in low-loss Si, rather than the relatively lossy III-V materials. We measure a received bit error rate (BER) of ${4.1} \times {{10}^{ - 3}}$4.1×10-3 when transmitting the 64-QAM data over an 80 km SMF using the hybrid Si/III-V laser. Furthermore, we measure a BER of $ {\lt} {1} \times {{10}^{ - 4}}$<1×10-4 with the Viterbi-Viterbi digital carrier phase recovery method when transmitting the 16-QAM data over an 80 km SMF using the hybrid Si/III-V laser. This performance is achieved at power penalties lower than those obtained with an exemplary distributed feedback laser and slightly higher than those with an exemplary narrow-linewidth external cavity laser.

Widely tunable, narrow linewidth external-cavity gain chip laser for spectroscopy between 1.0 - 1.1 µm.

We have developed and characterised a stable, narrow linewidth external-cavity laser (ECL) tunable over 100 nm around 1080 nm, using a single-angled-facet gain chip. We propose the ECL as a low-cost, high-performance alternative to fibre and diode lasers in this wavelength range and demonstrate its capability through the spectroscopy of metastable helium. Within the coarse tuning range, the wavelength can be continuously tuned over 30 pm (7.8 GHz) without mode-hopping and modulated with bandwidths up to 3 kHz (piezo) and 37(3) kHz (current). The spectral linewidth of the free-running ECL was measured to be 22(2) kHz (Gaussian) and 4.2(3) kHz (Lorentzian) over 22.5 ms, while a long-term frequency stability better than 40(20) kHz over 11 hours was observed when locked to an atomic reference.

Characterization of White and Flicker Frequency Modulation Noise in Narrow-Linewidth Laser Diodes

Frequency modulation noise of narrow-linewidth external cavity laser diodes is characterized in terms of power spectral density (PSD) using the recirculating delayed self-heterodyne method. The measured PSD is consistent with the oscillator noise model consisting of white and flicker noise. Based on this model, beat signal spectra observed in heterodyne measurements are derived, which explain well the delay- or observation time-dependent lineshape obtained in the experiments.

Mechanisms for inducing chaos in broad and narrow linewidth external-cavity laser diodes

Optical power spectra of two chaotic external-cavity diode lasers with different single mode linewidths are compared. We report what we believe is the first observation of a novel mechanism for the onset of chaos in broad linewidth external-cavity laser diodes.

Tunable, narrow-linewidth output from an injection-locked high-power AlGaAs laser diode array

An injection-locking technique has been employed to produce single-frequency tunable output from a high-power AlGaAs laser diode array. A narrow-linewidth external cavity laser is used as a master oscillator. With an injected power of 15 mW, a total output power of 1.0 W was obtained from the laser diode array with a spectral linewidth of less than 38 kHz, a wavelength tuning range of 13 nm, and a 0.67 degrees -wide single-lobed far-field beam.

Optical heterodyne transmission system with 565 Mbit/s DPSK modulation showing a receiver sensitivity of -53.3 dBm

Abstract A 565 Mbit/s DPSK heterodyne optical transmission system is discussed. A narrow linewidth external cavity laser is used as a transmitter laser. A bit error rate of 10−9 is achieved with a detected power of -53.3 dBm or 55 photoelectrons per bit.