We present an ultra-compact, hybrid faint pulse source (FPS) at 850 nm, making use of a linear eight VCSELs array at spectral (<1 pm wavelength difference, and >90% overlap at FWHM) and temporal (<1 ps) indistinguishability, as well as polarization quality in the four H/V/D/A BB84 channels >20 dB. A common VCSEL array on a single substrate is used, at a pitch of 250 μm and with integrated polarizers, having a spectral indistinguishability if the substrate is temperature levelled < 0.5 K. Each VCSEL represents either faint or full amplitude signal for the H/V/D/A channels of the BB84 protocol. The temperature levelling heatsink is made of Molybdenium, integrated on LTCC board to host the emitter substrate and its respective DAC driving circuit at speeds up to 10 GHz. VCSEL integrated micro-lenses and two additional micro-lens arrays fully collimate the beams and refocus them into a waveguide combiner chip which realizes the polarization independent coupling of all eight VCSEL free-space beams with a pulse delay variation <0.2 ps.
Fiber-based entangled photon sources are a key resource in emerging quantum technologies due to compactness, long-term stability and alignment-free operation. Fast control of the quantum state properties is also necessary in practical scenarios, where a universal source can be employed with different temporal and spectral configurations. Here, we report on a flexible source design that produces high-quality entanglement from continuous-wave up to GHz-pulsed operation modes. Our approach uses off-the-shelf optical components in a Sagnac configuration to generate polarization-entangled photon pairs at telecom wavelength. This design further allows phase modulation above MHz speeds with high fidelity. Together with its 60 nm spectral bandwidth, the proposed system is entirely suitable for wavelength-multiplexed and reconfigurable quantum networks, where state modulation or active bandwidth allocation is required.
Kerr resonators are simple and compact devices that enable ultrashort pulse and frequency comb generation over a wide range of wavelength and pulse parameters that are difficult to access with traditional mode-locked laser sources. Pulse generation in these systems derives from the formation of stable optical solitons. The pulse performance can be enhanced by exploiting novel classes of optical solitons. This talk will examine recently discovered cavity solitons in fiber Kerr resonators, including stretched-pulse and chirped pulse solitons. Stretched-pulse solitons in dispersion-managed systems enable record short pulses from Kerr resonators and chirped pulsed solitons in normal-dispersion cavities have the potential to stabilize much higher pulse energies. This talk will also examine the most recent results for pulse performance enhancement in stretched-pulse systems and the remarkable tolerance for dissipation of chirped-pulse Kerr resonator solitons.
Femtosecond mode-locked lasers are an important tool for the physical and life sciences. However, applications such as biomedical imaging require complex and expensive auxiliary systems to achieve desirable wavelengths and pulse repetition rates. In this talk I will discuss progress on the development of a complementary approach to femtosecond pulse generation based on fiber Kerr resonators. Recent experimental and theoretical results reveal a range of new phenomena including the shortest pulses observed to date from a fiber Kerr resonator
We introduce a toolbox for modelling laser diode operation over a large temperature range, as is encountered in long-pulse hair removal, and in mobile applications such as LiDAR. Power-to-current characteristics and lifetime estimations are sought for arbitrary pulse patterns in quasi-continuous-wave (QCW) operation. Our model is based on (1) the Zth-representation of the package thermal transient, (2) a temperature-dependent family of diode characteristics replacing the insufficient T0,T1-approach, and (3) the assumption that the device lifetime depends on the maximum junction temperature. The simulated evolution of output power and temperature is experimentally verified. Using our model, we assess the influence of the package geometry on the diode temperature and on the efficiency of diode-pumped solid state lasers. We also re-assess lifetime data, and derive safe operating parameters for an arbitrary pulse length.
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