Liqiang Yu

Monolithically Integrated Amplified Feedback Lasers for High-Quality Microwave and Broadband Chaos Generation

The dynamics of monolithically integrated amplified feedback lasers (AFL) is investigated through numerical simulation and experimental verification. The period-doubling route to chaos and high-frequency microwave generation are demonstrated through simulation. Then, we design and fabricate monolithically integrated AFLs. Mappings of dynamic states and oscillation frequency in the parameter space of phase section current IP and amplifier section current IA are depicted. For relative small IA, the period doubling evolution to chaos is presented with the increase of IP. For the relative large IA, a high-frequency mode-beating (M-B) pulsation can be observed under suitable value of IP. The oscillation frequency of period-one is about 10 GHz and the frequency of M-B pulsation is over 40 GHz for the device with a total length of 780 μm.

Widely Tunable Narrow-Linewidth Lasers Using Self-Injection DBR Lasers

A widely tunable distributed Bragg reflector (DBR) laser with kilohertz linewidth output is demonstrated using a dual-loop self-injection scheme. The self-injection-locked narrow linewidth DBR laser can be tuned by 13 nm, covering 18 channels, with side mode suppression ratios over 38 dB and linewidths all <;10 kHz.

Tunable optical microwave generation using self-injection locked monolithic dual-wavelength amplified feedback laser

A tunable optical microwave generation scheme using self-injection locked monolithic dual-wavelength amplified feedback laser (AFL) is proposed and experimentally demonstrated. By using a dual-loop feedback scheme, the 3-dB linewidth of the optical microwave output resulting from mode beating is reduced from MHz to kHz scale. Optical microwave generation tunable from 30 to 38 GHz with 3-dB linewidth below 2 kHz is experimentally demonstrated.

A Widely Tunable Directly Modulated DBR Laser With High Linearity

We demonstrate a widely tunable and high-modulation-bandwidth distributed Bragg reflector (DBR) laser. With the selected butt-joint material (λg = 1.44 μm) and butt-joint angle (45°) for the grating section, a widely tuning range of 13.88 nm with 19 consecutive channels is obtained for the two-section DBR laser. Furthermore, a small-signal modulation bandwidth of 16 GHz with in-band flatness of ±3 dB is realized at 10 °C. A uniform modulation bandwidth of more than 13 GHz is obtained for ten consecutive channels at 25 °C. Meanwhile, the DBR laser shows a high linearity, with an input 1-dB compression point of 17 dBm and an input third-order intercept point of 30 dBm at 13 GHz.

Widely Tunable Optical Decision Circuit Using a Monolithically Integrated SOA-SGDBR Laser

A widely tunable optical decision scheme using a monolithically integrated semiconductor optical amplifier-sampled-grating distributed Bragg reflector laser diode is proposed. Wavelength tunable optical decision is realized for both the cases of input wavelength detuning and output wavelength detuning. Within an input wavelength detuning range of 28 nm, or within an output wavelength detuning range of 24 nm, a maximum ON/OFF static contrast ratio of 42 dB over a 5-dB input power change is obtained. Dynamic performance up to 10 Gb/s is also demonstrated though numerical simulation using this scheme.

Wavelength and Mode-Spacing Tunable Dual-Mode Distributed Bragg Reflector Laser

In this letter, we report a novel mode-beating distributed Bragg reflector (DBR) laser with dual-mode output. Both the working wavelengths and mode spacing of the dual-mode laser can be tuned when the currents injected into the DBR laser are adjusted. The tuning ranges of the laser wavelength and mode-beating frequency are [1527.20 nm, 1531.04 nm] and [91.88 GHz, 94.02 GHz] , respectively. A fourth harmonic injection locking is also demonstrated to achieve a synchronized RF output at 93.23 GHz. The phase noise of the RF output is measured by using the down-conversion method. A single sideband phase noise of 96.92 dBc/Hz with 1-MHz offset at a down-converted frequency of 13.23 GHz is achieved.

A monolithically integrated dual-mode laser for photonic microwave generation and all-optical clock recovery

We demonstrate a monolithically integrated dual-mode laser (DML) with narrow-beat-linewidth and wide-beat-tunability. Using a monolithic DFB laser subjected to amplified feedback, photonic microwave generation of up to 45 GHz is obtained with higher than 15 GHz beat frequency tunability. Thanks to the high phase correlation of the two modes and the narrow mode linewidth, a RF linewidth of lower than 50 kHz is measured. Simulations are also carried out to illustrate the dual-mode beat characteristic. Furthermore, using the DML, an all-optical clock recovery for 40 Gbaud NRZ-QPSK signals is demonstrated. Timing jitter of lower than 363 fs (integrated within a frequency range from 100 Hz to 1 GHz) is obtained.

All-Optical Decision Gate With Extinction Ratio Improved Scheme Using an SOA-DBR Laser

A tunable all-optical decision scheme using a semiconductor optical amplifier integrated with a distributed Bragg reflector laser is proposed and simulated. Simulations show that the dynamic optical decisions with extinction ratio (ER) improvement from 28 to 6 dB can be obtained for signal rates between 1.25 and 10 Gb/s, respectively. In addition, with two input signals, logic NAND and NOR gates are realized with ER improvements of 24 and 20 dB, respectively.

Tunable Photonic Microwave Generation using Self-Injection-Locked Monolithic Dual-wavelength Semiconductor Laser

A tunable narrow-linewidth photonic microwave generation scheme using monolithic dual-wavelength amplified feedback laser under self-injection is proposed and demonstrated. Photonic microwave ranging from 29 to 37.6 GHz with linewidth below 4 kHz is realized.

LATERAL-mode-beating for Terahertz excitation in 1.5-µM DBR laser

We report a Terahertz (THz) excitation source based on a dual-lateral-mode ridge-waveguide Distributed Bragg Reflector laser (DBR) with an optimized 4 μm ridge width in the 1.5-μm range. Dual-lateral-mode generation and beating are verified experimentally. In the experiments, Terahertz signals of 1.133 THz, 1.134 THz, 1.235 THz and 1.24 THz are obtained under different bias conditions. The two wavelengths can be tuned continuously with small strength difference (<; 5 dB) and high side-mode suppression ratio ( SMSR > 45 dB).