The transition from frequency-modulated to amplitude-modulated frequency comb operation is studied experimentally in a multi-section InAs/InGaAs quantum dot frequency comb laser. Temporally and spectrally-resolved intensity and phase as well as time and frequency domain analysis allow to identify frequency-modulated and amplitude-modulated comb operation regimes in dependence on the laser gain current and absorber reverse bias voltage.
Optical self-injection stabilization of a passively mode-locked InGaAs double quantum well semiconductor laser is reported. Time-domain, frequency-domain and spectral domain measurement results in dependence on feedback strength and feedback delay demonstrate pulse width and higher harmonic mode-locking control. Traveling-wave equation simulations allow to explain the measured sequence of harmonic mode-locking orders in dependence on the feedback strength and delay.
An amplitude-modulated optical frequency comb generated by a passively mode-locked InGaAs double quantum well semiconductor laser is optically injected into a laser emitting a single optical mode continuous wave output in solitary operation. Optical frequency comb generation in the injected laser is experimentally demonstrated and regimes of injection locking are analyzed.
Electrical injection locking dynamics of a monolithic edge-emitting semiconductor quantum dash frequency comb laser are investigated experimentally by beat note spectroscopy. Spectrally resolved phase and amplitude characteristics across the 10 nm broad optical comb spectra and an inter-mode beat frequency locking dynamics are reported. A locking range of 2 MHz around the fundamental repetition rate of 20 GHz and an inter-mode beat line width reduction to the line width of the electrical radio-frequency signal source are attained.
In this paper we review our recent progress on high performance mode locked InAs quantum dot lasers that are directly grown on CMOS compatible silicon substrates by solid-source molecular beam epitaxy. Different mode locking configurations are designed and fabricated. The lasers operate within the O-band wavelength range, showing pulsewidth down to 490 fs, RF linewidth down to 400 Hz, and pulse-to-pulse timing jitter down to 6 fs. When the laser is used as a comb source for wavelength division multiplexing transmission systems, 4.1 terabit per second transmission capacity was achieved. Self-mode locking is also investigated both experimentally and theoretically. The demonstrated performance makes those lasers promising light source candidates for future large-scale silicon electronic and photonic integrated circuits (EPICs) with multiple functionalities.
Interband cascade laser (ICL) optical frequency combs are promising midwave infrared sources for dual comb spectroscopy probing the strong fundamental absorption lines of numerous chemical and biological agents. In this work, a 4-mm-long ICL frequency comb emitting at 3.3 μm was operated by single-cavity optical self-injection. The experiments employing a free-space optical self-injection length of 1.1m with fine-delay control demonstrated a tuning range of 119MHz around the free-running intermode beat frequency of 9.58 GHz. For resonant fine-delay the line width of the intermode beat frequency was reduced to 390 kHz, what is an improvement by a factor of 40 in comparison to the solitary laser line width.
Passively mode-locked InAs/InGaAs quantum dot on silicon lasers emitting at 1310nm are promising sources for high-speed high-capacity communication applications. Optical self-injection stabilization of a monolithic passively mode-locked quantum dot on Silicon laser with an absorber section length to total length ratio of 18% is investigated experimentally. A repetition rate tuning range of 24MHz around the free-running repetition rate of 9.4 GHz and a pulse-to-pulse timing jitter reduction by a factor of 2.5 from 150 fs to 59 fs are achieved for an external optical cavity length of 5.8m with fine-delay control. Obtained experimental results are in good quantitative agreement with simulation results obtained by a stochastic time-domain model.
Timing stabilization of a photonic integrated circuit extended cavity passively mode-locked semiconductor ring laser with four gain sections and two saturable absorbers in a symmetric ring geometry by optical self-injection is presented. The laser has been fabricated using an InP generic integration technology platform. Repetition rate tuning up to 5.5MHz and a timing jitter reduction by optical self-injection from 99 fs (solitary laser operation) to 20 fs is demonstrated. The experimental results are in excellent agreement with results obtained by a stochastic time domain model which yet had been solely applied to edge-emitting straight waveguide semiconductor lasers.
Intermode beat frequency and line-width stabilization of a 1 mm long self mode-locked frequency comb quantum dash laser emitting at 1535 nm by external all-fiber based single-cavity optical self-injection time-delay control is presented. Self-injection optical delay tuning is conducted by piezo-crystal single-mode fiber stretching. An intermode beat frequency control by 2 MHz and an intermode beat frequency line width reduction from 67 kHz to approximately 900 Hz is achieved. The experimental results are confirmed by an independent free-space stabilization experiment and stochastic time-domain modeling.
We experimentally study the emission dynamics of a monolithic multi-section semiconductor laser based on InAs/InGaAs quantum dot (QD) material in the regime of passive mode-locked (ML) operation obtained via saturable losses in the absorber (reversed biased). When the active section is biased above the lasing threshold we observe emission of a regular train of optical pulses at 1250nm with characteristic repetition rate of 6 GHz. By sweeping back the pump current below lasing threshold, we verify that the ML solution coexists with the zero intensity ("off") solution, even in absence of any external optical injection.1 These evidences are very promising for the observation of temporal localized structures in compact, monolithic semiconductor photonics devices. Experimental results are validated by numerical simulations performed using a multi-section delayed differential equation (DDE) model to compute the evolution of the electrical field, coupled with the rate-equations that describe the carrier dynamics in the QD active and absorber media.
In this contribution we investigate experimentally and by modeling the mode spacing tuning range and stability of optical frequency comb lines generated by a 1 mm long self mode-locked single section quantum dot semiconductor laser subject to dual-cavity all optical self-feedback. The external optical feedback cavities have an optical length of 9.4 m and 16.5 m and are implemented by optical fibers. The optical feedback strengths are below 0.02% back reflected onto the as-cleaved laser facet. The line-width of the laser mode-beating frequency equals optical frequency mode spacing of 40.67 GHz amounts to 1.4 MHz in the free-running case. By fine-delay tuning of both optical feedback lengths, we find a comb-line spacing tuning range of 70 MHz. The radio-frequency linewidth decreases by a factor of 700 down to 2 kHz for particular adjusted optical feedback cavity lengths, thus improve the mode spacing stability. We validate the experimental findings by a simple and universal stochastic time-domain model.
Monolithic passively mode-locked (PML) semiconductor lasers with multi-GHz repetition rate (RR) emitting at wavelengths of around 1070nm are attractive ultrafast sources for seeding ytterbium doped fiber amplifiers and for photonic communication at high data rates. The timing stability quantified by the timing jitter (TJ) and the RR tuning range of a PML multi quantum-well (QW) semiconductor laser emitting at 1070nm subject to dual-cavity optical self-feedback (DC-OFB) consisting of one very short cavity for a high RR tuning range and one very long cavity for strong TJ reduction is investigated. The 3mm long PML QW semiconductor laser with a saturable absorber section length of 10% of the total cavity length has a RR of 13.61 GHz and a TJ of 83 fs with a pulse width amounting to 8 ps at the investigated injected gain current, absorber reverse bias voltage and cooling block temperature. For the combination of the long fiber-based cavity amounting to 5.9m combined with the short free-space cavity amounting to a few laser cavity lengths a RR tuning range over 1 GHz is achieved. Furthermore a minimal TJ of approximately 330 as with full sideband suppression in the radio-frequency (RF) spectrum is achieved which is an improvement by factor 250 in comparison to the free-running laser.
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