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Single-mode diode lasers on an InP(001) substrate have been developed using InAs/In0.53Ga0.47As quantum dash (Qdash) active regions and etched lateral Bragg gratings. The lasers have been designed to operate at wavelengths near 2 lm and exhibit a threshold current of 65mA for a 600 lm long cavity, and a room temperature continuous wave output power per facet >5mW. Using our novel growth approach based on the low ternary In0.53Ga0.47As barriers, we also demonstrate ridge-waveguide lasers emitting up to 2.1 lm and underline the possibilities for further pushing the emission wavelength out towards longer wavelengths with this material system. By introducing experimentally the concept of high-duty-cycle lateral Bragg gratings, a side mode suppression ratio of >37 dB has been achieved, owing to an appreciably increased grating coupling coefficient of j~40 cm-1. These laterally coupled distributed feedback (LC-DFB) lasers combine the advantage of high and well-controlled coupling coefficients achieved in conventional DFB lasers, with the regrowth-free fabrication process of lateral gratings, and exhibit substantially lower optical losses compared to the conventional metal-based LC-DFB lasers. [ABSTRACT FROM AUTHOR]

Laser-based light detection and ranging (LiDAR) is key to many applications in science and industry. For many use cases, compactness and power efficiency are key, especially in high-volume applications such as industrial sensing, navigation of autonomous objects, or digitization of 3D scenes using hand-held devices. In this context, comb-based ranging systems are of particular interest, combining high accuracy with high measurement speed. However, the technical complexity of miniaturized comb sources is still prohibitive for many applications, in particular when high optical output powers and high efficiency are required. Here we show that quantum-dash mode-locked laser diodes (QD-MLLD) offer a particularly attractive route towards high-performance chip-scale ranging systems. QD-MLLDs are compact, can be easily operated by a simple DC drive current, and provide spectrally flat frequency combs with bandwidths in excess of 2 THz, thus lending themselves to coherent dual-comb ranging. In our experiments, we show measurement rates of up to 500 MHz—the highest rate demonstrated with any ranging system so far. We attain reliable measurement results with optical return powers of only – 40 dBm, corresponding to a total loss of 49 dB in the ranging path, which corresponds to the highest loss tolerance demonstrated so far for dual-comb ranging with chip-scale comb sources. Combing QD-MLLDs with advanced silicon photonic receivers offers an attractive route towards robust and technically simple chip-scale LiDAR systems. [ABSTRACT FROM AUTHOR]

The new paradigm of parity-time symmetry in quantum mechanics has readily been applied in the field of optics with numerous demonstrations of exotic properties in photonic systems. In this work, we report on the implementation of single frequency electrically injected distributed feedback (DFB) laser diodes based on parity-time symmetric dual gratings in a standard ridge waveguide configuration. We demonstrate enhanced modal discrimination for these devices as compared with index or gain coupled ones, fabricated in the same technology run. Optical transmission probing experiments further show asymmetric amplification in the light propagation confirming the parity-time symmetry signature of unidirectional light behavior. Another asset of these complex coupled devices is further highlighted in terms of robustness to optical feedback. [ABSTRACT FROM AUTHOR]

Temperature- and field-dependent electron and hole mobilities were simultaneously derived from admittance measurements on an InP/InGaAsP/InAs/InP long wavelength laser structure. Each carrier’s mobility was separated in the frequency domain due to the corresponding different relaxation times from C versus log f curves. Derived electron and hole mobilities followed the Poole–Frenkel-type field dependence, indicating the transport of carriers through hopping. Extracted thermal energy gap ( \Delta ) and disorder temperature ( T0 ) values were in mutual agreement with previous current density–voltage measurements and from the energy band diagram of the present structure, constructed from other studies in the literature by photoluminescence and photoluminescence excitation experiments. [ABSTRACT FROM PUBLISHER]

Laser diodes with optical feedback can exhibit periodic intensity oscillations at or near the relaxation-oscillation frequency. We demonstrate optoelectronic oscillators based on external-cavity semiconductor lasers in a periodic dynamical regime tunable over the entire $X$ -band. Moreover, unlike standard optoelectronic oscillators, we need not employ the time-dependent optical intensity incident on a photodiode to generate the microwave signal, but rather have the option of generating the electrical microwave signal directly as a voltage V(t)$ at the laser-diode injection terminals under constant current operation; no photodiode need be involved, thus circumventing optical-to-electrical conversion. We achieve a timing jitter of \lesssim 10$ ps and a quality factor of across the entire $X$ -band, that ranges from 6.79 to 11.48 GHz. Tuning is achieved by varying the injection current $J$ . [ABSTRACT FROM AUTHOR]

We investigate the amplitude and phase noise of an optical frequency comb based on InAs/InP quantum-dash mode-locked laser. The laser demonstrates low relative intensity noise (< −125 dB/Hz) and phase noise in the passive mode-locking regime. By actively mode-locking the laser, we observe a reduction in the flicker FM noise and timing jitter, as a result of which the optical linewidth decreases, and hence the effective bandwidth compatible with optical coherent systems increases by more than 50% to $\sim 1.1$ THz. [ABSTRACT FROM PUBLISHER]

A multi-GHz chaotic optoelectronic oscillator based on an external cavity semiconductor laser (ECL) is demonstrated. Unlike the standard optoelectronic oscillators for microwave applications, we do not employ the dynamic light output incident on a photodiode to generate the microwave signal, but instead generate the microwave signal directly by measuring the terminal voltage V(t) of the laser diode of the ECL under constant-current operation, thus obviating the photodiode entirely. [ABSTRACT FROM AUTHOR]

The properties of InP/InGaAsP/InAs/InP laser structure, mainly used in the fiber optic telecommunication industry, were investigated through current density-voltage- temperature ( $J$ – $V$ – $T$ ) measurement within dark and light conditions. Tunneling and generation-recombination carrier conduction mechanisms were identified within a junction bias voltage of 0–0.6 V. Above 0.6 V, Poole–Frenkel was the actual path in conduction and the mobility of carrier was determined quantitatively by means of temperature-dependent $J$ – $V$ curves in the space charge bias region. A thermal energy gap of 0.8 eV corresponded to the band gap of quantum dashes in which radiative recombination took place to emit a laser light at 1550 nm. [ABSTRACT FROM AUTHOR]

In this paper, we present a systematic investigation of passive mode-locked InAs/InP quantum-dash lasers in terms of frequency and timing stability. Mode-locking features are analyzed using the frequency domain approach based on the concept of supermodes. It is shown that the phase of adjacent longitudinal modes is correlated over 1.3-THz frequency span. The observed strong coherence between modes enables low timing jitter and a long-term stability of the repetition rate frequency within 5×10-8 over 100 s. [ABSTRACT FROM PUBLISHER]

We introduce a novel scheme for the simultaneous reduction of time-bandwidth product (TBP) and RF linewidth of quantum-dash two-section mode-locked lasers using optical injection-locking and filtered optical feedback. The optical injection-locked laser, double-locked with optical feedback showed 2\!\!\times TBP reduction and RF linewidth reduction by two orders of magnitude. This stabilization technique is implemented in an all-optical arrangement without optical/electrical conversion which is ideal for high-repetition-rate devices and photonic integration. [ABSTRACT FROM PUBLISHER]

P-doped quantum dash based lasers have shown superior dynamic performance as compared to their un-doped counterparts. This improvement in performance is strongly observed in line-width enhancement factor. These devices show a dramatic reduction in the αH parameter, resulting in very low chirp. This letter discusses the nature line-width enhancement factor of p-doped quantum dash lasers as opposed to un-doped counterparts. Owing to the p-doping a low and bias-stable alpha parameter is demonstrated. [ABSTRACT FROM AUTHOR]

We report optical injection-locking in 21-GHz single-section and two-section InAs/InP 1.5-\mu\m quantum-dash mode-locked lasers. Two distinct mode-locked regimes were observed and successfully locked to the optically injected light. The single-section laser only operates as a self-mode-locked laser while the two-section laser could operate as both a self-mode-locked laser and saturable-absorber dominated mode-locked laser. The continuous-wave (CW) injection-locked self-mode-locked laser shows wide tuning of the mode-locked frequency (\approx270 MHz) within the locking range. The CW injection-locked saturable-absorber dominated mode-locked laser demonstrates wide optical spectrum, and 5.5 \times reduction in the time-bandwidth product of the pulses. Using dual-mode injection, strong reduction of timing jitter (\approx235 fs) is possible leading to the generation of a wide coherent frequency comb. Coherence between all the modes and the master laser is confirmed by measuring the RF beat note of each mode with a narrow linewidth laser. [ABSTRACT FROM PUBLISHER]

We analyze the relaxation dynamics of quantum dot/dash lasers in terms of the energy exchange between the ground state and the wetting layer. We consider the case where both capture and escape times are of the same order of magnitude and determine the relaxation oscillation frequency and its damping rate. We show that the escape process may significantly affect the modulation characteristics and the tolerance to optical feedback. [ABSTRACT FROM AUTHOR]

We report on low-temperature cross-sectionalscanning tunneling microscopy and spectroscopy on InAs(P)/InGaAsP/InP(001)quantum dashes, embedded in a diode-laser structure. The laser activeregion consists of nine InAs(P) quantum dash layers separated by theInGaAsP quaternary alloy barriers. The effect of the p-i-n junctionbuilt-in potential on the band structure has been evidenced and quantifiedon large-scale tunneling spectroscopic measurements across the wholeactive region. By comparing the tunneling current onset channels,a consistent energy shift has been measured in successive quantumdash or barrier layers, either for the ground state energy of similar-sizedquantum dashes or for the conduction band edge of the barriers, correspondingto the band-bending slope. The extracted values are in good quantitativeagreement with the theoretical band structure calculations, demonstratingthe high sensitivity of this spectroscopic measurement to probe theelectronic structure of individual nanostructures, relative to localpotential variations. Furthermore, by taking advantage of the potentialgradient, we compared the local density of states over successivequantum dash layers. We observed that it does not vanish while increasingenergy, for any of the investigated quantum dashes, in contrast towhat would be expected for discrete level zero-dimensional (0D) structures.In order to acquire further proof and fully address the open questionconcerning the quantum dash dimensionality nature, we focused on individualquantum dashes obtaining high-energy-resolution measurements. Thestudy of the local density of states clearly indicates a 1D quantum-wirelikenature for these nanostructures whose electronic squared wave functionswere subsequently imaged by differential conductivity mapping. [ABSTRACT FROM AUTHOR]