We investigate the interwoven dynamic evolutions of neutral nitrogen molecules together with nitrogen ions created through transient tunnel ionization in an intense laser field. By treating the molecules as open quantum systems, it is found that considering real-time injection of ions and strong couplings among their electronic states, nitrogen molecular ions are primarily populated in the electronically excited states, rather than staying in the ground state as predicted by the well-known tunneling theory. The unexpected result is attributed to sub-cycle switch-on of timedependent polarization by transient ionization and dynamic Stark shift mediated near-resonant multiphoton transitions. Their combined contribution also causes that the vibrational distribution of N + 2 does not comply with Franck-Condon principle. These findings corroborate the mechanism of nitrogen molecular ion lasing and are likely to be universal. The present work opens a new route to explore the important role of transient ionization injection in strong-field induced non-equilibrium dynamics.The fundamental process of strong field ionization of atoms by intense ultrashort laser pulses occurs at attosecond timescale [1-3] and lasts for pulse lengths in femtoseconds. The temporal confined strong field ionization (SFI) creates broad bandwidth non-stationary ionic states along with launching of attosecond electron wavepacket forming the foundation of attoseond physics [4][5][6][7][8]. One of the key problem is how the coherence of the ionic states affect the subsequent ultrafast nonequilibrium evolution ranging from charge migration in molecules [9], electron transport in condense matter [10] to ultrafast laser processing of materials [11]. It is particular intriguing to question wether the further interaction of the ions with lasers can be considered independently by assuming the prior ionization is completed?Recent experiments indicate that the interplay of subcycle SFI and the followed ion-laser coupling is indispensable for nitrogen molecular ion lasing [12][13][14][15][16] which suggests the new possibility to manipulate the ion coherence upon its creation toward ion-based quantum optics. While SFI itself can be described well by the celebrated Keldysh tunneling theory [17], a complete model treating both ionization of neutrals and laser-ion couplings on the equal footing is still lacking. Theoretically, dealing with bounded multi-electron problem is already a difficult task, it is even challenging for open quantum many-body systems when ionization is involved. Exact time-dependent multilelectron theories are limited to two electrons cases [18] or struggling with ionization-induced derivative discontinuities in density-functionals [19]. A lot of theoretical works have devoted to the coherent ionic evolution in a multi-channel formalism [20,21] but the ion-laser coupling within the ionization process remains elusive.The current work attempts to address the fundamental question of how the transient SFI will influence the quantum states of th...

Optical proximity communication (OPxC) with reflecting mirrors is presented. Direct optical links are demonstrated for silicon chips with better than -2.5dB coupling loss, excluding surface losses. OPxC is a true broadband solution with little impairment to the signal integrity for high-speed optical transmission. With wavelength division multiplexing (WDM) enabled OPxC, very high bandwidth density I/O, orders of magnitude higher than the traditional electrical I/O, can be achieved for silicon chips.

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Supercontinuum (SC) light sources hold versatile applications in many fields ranging from imaging microscopic structural dynamics to achieving frequency comb metrology. Although such broadband light sources are readily accessible in the visible and near infrared regime, the ultraviolet (UV) extension of SC spectrum is still challenging. Here, we demonstrate that the joint contribution of strong field ionization and quantum resonance leads to the unexpected UV continuum radiation spanning the 100 nm bandwidth in molecular nitrogen ions. Quantum coherences in a bunch of ionic levels are found to be created by dynamic Stark-assisted multiphoton resonances following tunneling ionization. We show that the dynamical evolution of the coherence-enhanced polarization wave gives rise to laser-assisted continuum emission inside the laser field and free-induction decay after the laser field, which jointly contribute to the SC generation together with fifth harmonics. As proof of principle, we also show the application of the SC radiation in the absorption spectroscopy. This work offers an alternative scheme for constructing exotic SC sources, and opens up the territory of ionic quantum optics in the strong-field regime.

We report on an experimental investigation of the five vibrational Raman lines at 358 nm, 388 nm, 391 nm, 428 nm, and 471 nm of N 2 + resonantly driven by the self-seeding ionic lasers generated by a polarization-modulated (PM) or alternatively a linearly polarized (LP) femtosecond laser. It was found that the spectral intensities of several Raman lines can be dramatically enhanced by exploiting the PM laser pulses in comparison to the LP laser pulses. The evaluated Raman conversion efficiency reaches ∼ 1 0 − 2 for some lasing lines at suitable pressures. Moreover, the role of interplay between the seed amplification and the resonant vibrational Raman scattering processes in inducing the gain of N 2 + lasing is characterized for the first time. The developed vibrational Raman spectroscopy with intense ultrafast lasers provides an additional approach to interrogate the products in a femtosecond filament, and it therefore can be a powerful tool for identifying chemical species at remote distances in the atmosphere.

Semiconductor microlasers with an equilateral triangle resonator (ETR) are analyzed by rate equations with the mode lifetimes calculated by the finite-difference time-domain technique and the Padé approximation. A gain spectrum based on the relation of the gain spectrum and the spontaneous emission spectrum is proposed for considering the mode selection in a wide wavelength span. For an ETR microlaser with the side length of about 5 m, we find that single fundamental mode operation at about 1.55 m can be obtained as the side length increases from 4.75 to 5.05 m. The corresponding wavelength tuning range is 93 nm, and the threshold current is about 0.1 to 0.4 mA.

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