K.T. Tan

35GHz mode-locking of 1.3μm quantum dot lasers

35GHz passive mode-locking of 1.3μm (InGa)As∕GaAs quantum dot lasers is reported. Hybrid mode-locking was achieved at frequencies up to 20GHz. The minimum pulse width of the Fourier-limited pulses was 7ps with a peak power of 6mW. Low uncorrelated timing jitter below 1ps was found in cross correlation experiments. High-frequency operation of the lasers was eased by a ridge waveguide design that includes etching through the active layer.

Direct modulation and mode locking of 1.3 μm quantum dot lasers

We report 7 GHz cut-off frequency, 2.5 and 5 Gb s−1 eye pattern measurements upon direct modulation of 1.3 μm quantum dot lasers grown without incorporating phosphorus in the layers. Passive mode-locking is achieved from very low frequencies up to 50 GHz and hybrid mode-locking is achieved up to 20 GHz. The minimum pulse width of the Fourier-limited pulses at 50 GHz is 3 ps, with an uncorrelated timing jitter below 1 ps. The lasers are optimized for high frequency operation by a ridge waveguide design that includes etching through the active layer and ridge widths down to 1 μm. The far-field shape for 1 μm is close to circular with a remaining asymmetry of 1.2.

High bit rate and elevated temperature data transmission using InGaAs quantum-dot lasers

A 5-Gb/s data modulation and transmission is investigated using Fabry-Pe/spl acute/rot InGaAs quantum-dot lasers emitting at approximately 1.3 /spl mu/m. Error-free transmission of 5-Gb/s data at room temperature over 4 km of single-mode fiber (SMF) and over 500 m of installed grade multimode fiber are demonstrated for the first time. The temperature dependence of the data modulation performance is also studied. We report error-free 2.5-Gb/s data modulation up to 50/spl deg/C and transmission over 4 km of SMF with a Q-factor penalty of 0.5 dB. Error-free 5-Gb/s data modulation is observed up to 30/spl deg/C and 5-Gb/s data transmission over 4 km of SMF with a Q-factor penalty of 0.8 dB is obtained at 40/spl deg/C. The lack of overshoot and ringing in the eye diagrams is attributed to the large damping factor observed under small-signal modulation.

Mode-locked quantum dot lasers for picosecond pulse generation

In this work we present a detailed study of picosecond optical pulse generation using high-repetition rate mode-locked quantum dot lasers. MOCVD-grown quantum dot lasers emitting at 1.1μm and MBE-grown quantum dot lasers emitting at 1.3μm are investigated. Passive mode-locking at 10GHz, 18GHz and 36GHz with pulse widths in the 6-12ps range are reported. Hybrid mode-locking is demonstrated at 10GHz, showing a significant improvement in the RF spectral characteristics when compared with passive mode-locking. A timing jitter of 600fs (2.5MHz to 50MHz) is measured in the 18GHz passively mode-locked laser. Autocorrelation techniques are used to characterise the high repetition rate mode-locked lasers as well as the time-bandwidth product of the optical pulses. Fourier-transform limited pulses are obtained from passively mode-locked QD lasers.

Investigation of high repetition rate mode-locked quantum dot lasers

Passive mode-locking of quantum dot laser at 18 GHz is reported for the first time. The generation of reduced jitter, Fourier transform limited pulses is also investigated through passive and hybrid mode-locking at 10 GHz.

High bandwidth modulation of multiple contact 1.3 micron quantum dot lasers

By forming twin contacts on a 1300 nm quantum dot laser, a small signal modulation bandwidth of 4.6 GHz is achieved. This bandwidth value is 2.3 times greater than that for the equivalent single contact device. The quantum dot lasers studied are 800 /spl mu/m long with 8 /spl mu/m wide ridge guides and 5 InAs quantum dot stacks in the active layer.

Mode locking of InGaAs quantum dot lasers

Extensive mode-locking investigations are performed in InGaAs/InAs/GaAs quantum dot (QD) lasers. Monolithic mode-locked lasers are fabricated using QD material systems grown by MOCVD and MBE techniques and emitting at 1.1μm and 1.3μm, respectively. The mode-locking performance is evaluated using a variety of laser designs, with various ridge waveguide geometries, cavity and absorber lengths. Passive and hybrid mode-locking are studied and compared in 3.9mm long devices emitting at 1.1μm and operating at a repetition rate of 10GHz. Using 2.1mm long devices emitting at 1.3μm, 18GHz passive mode locking with 10ps Fourier transform limited pulses is demonstrated. This confirms the potential of quantum dot laser for low chirp, short optical pulse generation. Preliminary investigation of the timing jitter of QD passively mode-locked lasers and the behaviour of the QD absorber are also presented. Finally, we report 36GHz passive mode-locking with 6ps optical pulse obtained using 1.1mm long QD lasers emitting at 1.3μm.