High-channel-count 20  GHz passively mode-locked quantum dot laser directly grown on Si with 41  Tbit/s transmission capacity

Abstract

Low cost, small footprint, highly efficient and mass producible on-chip wavelength-division-multiplexing (WDM) light sources are key components in future silicon electronic and photonic integrated circuits (EPICs) which can fulfill the rapidly increasing bandwidth and lower energy per bit requirements. We present here, for the first time, a low noise high-channel-count 20 GHz passively mode locked quantum dot laser grown on complementary metaloxide-semiconductor compatible on-axis (001) silicon substrate. The laser demonstrates a wide mode locking regime in the O-band. A record low timing jitter value of 82.7 fs (4 -80 MHz) and a narrow RF 3-dB linewidth of 1.8 kHz are measured. The 3 dB optical bandwidth of the comb is 6.1 nm (containing 58 lines, with 80 lines within the 10 dB bandwidth). The integrated average relative intensity noise values of the whole spectrum and a single wavelength channel are − 152 dB/Hz and − 133 dB/Hz in the frequency range from 10 MHz to 10 GHz, respectively. Utilizing 64 channels, an aggregate total transmission capacity of 4.1 terabits per second is realized by employing a 32 Gbaud Nyquist four-level pulse amplitude modulation format. The demonstrated performance makes the laser a compelling on-chip WDM source for multi-terabit/s optical interconnects in future large scale silicon EPICs.

Passively mode-locked semiconductor quantum dot on silicon laser with 400 Hz RF line width

“…Measurements without the use of the booster optical amplifier have shown that neither the −3 dB spectral width nor the timing jitter is influenced by the booster optical amplifier, only the baseline for L(f) at −120 dBc/Hz is increasing due to the lower power impinging onto the detector. The lowest identified value of 9 fs for the pulse-to-pulse timing jitter for this laser is 1.5 times higher than the one for the lowest timing jitter obtained so far by a passively mode-locked quantum dot laser on silicon of 6 fs at 20 GHz with a 1.6 times broader pulse width at this operation point [1] than the device presented in this work. in this area for nonlinear intensity auto-correlation.…”

“…In literature, line widths of 100 kHz (−3 dB) for a self mode-locked quantum dot laser on silicon [36] and 80 kHz for a similar device presented here [35] were reported indicating a 200-250 times broader repetition rate line width as compared to the here presented results although no precise pulse train stability analysis in terms of radio-frequency line width has been carried out yet for these devices. Additionally, in the results presented here, a 2.75 times narrower repetition rate line width is observed as compared to the reported repetition rate line width of 1.1 kHz from a complex tapered waveguide design from a silicon quantum-well laser [34] and 4.5 times narrower line width compared to the 1.8 kHz width reported for a monolithic InAs quantum dot passively mode-locked two-section laser on silicon [1]. Comparing the achieved timing stability with quantum dot passively mode-locked lasers on native substrates, except of silicon, repetition rate line widths ranging from 500 Hz up to 27 kHz [37,[39][40][41][42][43] have been reported.…”

“…Optical frequency comb passively mode-locked semiconductor quantum dot lasers directly grown on silicon are ideal sources for applications including high data rate optical communication applications in the O-band [1][2][3][4][5], spectroscopic sensing on a silicon photonics chip [6], dual-comb spectroscopy [7] and for silicon-chip based ultra-fast optical oscilloscopes [8]. Mode-locked quantum dot semiconductor lasers offer small size, higher functionality and lower energy consumption photonic integrated circuits on silicon, the material of choice for the photonics industry [2][3][4][9][10][11][12][13][14][15].…”

“…Subsequently, self mode-locking operation of a quantum dot on silicon laser without the need of any saturable absorber generated 490 fs short optical pulses has been reported at a repetition rate of 31 GHz and a repetition rate line width of 100 kHz [36]. The lowest repetition rate line width of a passively mode-locked quantum dot laser directly grown on silicon amounts to date to 1.8 kHz at a repetition rate of 20 GHz [1]. Shortest generated optical pulses from monolithic passively mode-locked quantum dot lasers grown on native substrates, except of silicon, are 360 fs [37] with a tapered waveguide design and 393 fs [38] for a two-section straight waveguide laser and 493 fs for a tapered three-section waveguide design [39].…”

Optical Injection-locked High-speed Heterogeneous Quantum-dot Microring Lasers

“…Inhomogeneous broadening effect in self-assembled QD structure effectively broadens the optical gain bandwidth. It can enable widely tunable single-wavelength lasers [3] and large comb width to fit more wavelength channels [15]. But it also can easily support multiple longitudinal mode lasing in lasers without a fine wavelength selection mechanism, such as microring lasers whose lasing mode space is only determined by laser cavity free spectral range (FSR).…”