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We fabricated ultra-thin glass cantilevers using femtosecond laser pulses while integrating nitrogen vacancy (NV) centers at its tip. The magneto-mechanical coupling of electron spins in integrated NV center’s was exploited for quantum sensing applications.

We fabricated ultra-thin glass cantilevers using femtosecond laser pulses while integrating nitrogen vacancy (NV) centers at its tip. The magneto-optical susceptibility of NV centers towards electron spin was exploited for quantum sensing applications.

High harmonic generation (HHG) is strongly modified near plasmonic nanostructures due to confinement and inhomogeneity of the electromagnetic field. Previous studies have revealed low-intensity generation of HHG and extension of the plateau; however, the roles of potential shape and a combination of inhomogeneous infrared (IR) and blue fields on HHG have not been studied. In this work, we study HHG driven by inhomogeneous two-color (800–400 nm) IR and blue femtosecond pulses by numerically solving the time-dependent Schrödinger equation. HHG spectra are computed for two different models: for a short-range potential, which supports a single-bound state, and for a long-range potential, which supports a Rydberg series, to show potential dependence on inhomogeneous two-color HHG. A substantial enhancement in the value of the cut-off resulting from inhomogeneity up to the ∼600th order, extending beyond the water window, is found for both the models. The HHG spectra are highly sensitive to the relative phase of the two-color fields and this sensitivity increases with increasing inhomogeneity. Possibilities of efficiently generating and controlling attosecond pulse train and isolated attosecond pulse are discussed.

We demonstrate a simple and versatile nanomechanical force measuring setup with 1 nN precision in air and vacuum using a load cell of an ultra-microbalance. We validate stability, precision, and linearity of the load cell with simple tests. The setup is customized to measure stress-strain response of biomaterials (silk, leaf, and flower) and capillary force in fluids. We isolated an optical pull force induced by a Watt-level laser reflected from a mirror/solid surface in air, in addition to optical push force. Furthermore, we add an interferometric probe to directly measure nanoscale deflection of cantilever of the load cell in real-time, thus bypassing its conventional electromagnetic readout, to improve speed and precision of the instrument. We demonstrate nanomechanical force measurement in high vacuum with the same precision and employ radiation pressure to calibrate the load cell for various precision measurements.

Optical methods to study the laser-matter interactions precisely is of utmost importance. Here, we demonstrate a simple, collinear interferometer with minimum components to study time-resolved thermal deformations induced in solids /thin films with a picometer resolution. We have measured sub-nm deformations in various samples, like red acrylic sheet, when exposed to high-power CW laser source. The displacement measurement from our interferometer was then used to calculate the change in temperature of the solid sample. The minimum temperature change recorded was $(41.96\pm 5.78) mK$. Precise temperature change of solid materials is needed in many applications like in laser heating or cooling experiments. It will be interesting to study the thermal deformation in solids due to ultra-fast nano-second or pico-second laser pulses.

Interaction of light with fluid produces many competing phenomena at the nanoscale, which are less well understood due to the lack of picometer precision in measuring optofluidic deformation. Here, we employ a microliter sessile fluid drop as a self-stabilized laser microinterferometer and resolve its nanoscale interface dynamics, with precisions of about 600 pm in real-time and 20 pm with a modulated beam, below the thermal limit. For evaporating droplets having various absorbance values, we isolate a nanodimple due to laser heating from the nanobump induced by Minkowski's optical momentum transfer. We model the dimple as resulting from a negative surface-tension thermal gradient induced by nonuniform local temperature variation, which we resolved with unprecedented 600 nK precision, besides detecting pN level radiation pressure force at the transparent fluid interface. These signatures are generic for a wide variety of fluids including Au-nanoparticle suspension, olive oil, glycerine, and biofluids such as egg-white and human saliva. Our study opens a route to achieve picometer precision with tiny fluid samples for intriguing applications.

We investigate the dissociation dynamics of diatomic molecules subjected to both a femtosecond infrared (IR) laser pulse and a femtosecond pulse train (FPT) within the framework of the Morse potential model. When the IR and FPT are phase delayed, we observe well-resolved oscillations in dissociation probability, corresponding to multiple integers of the IR period, exhibiting enhancement and suppression of bond dissociation. These oscillations reveal a rich dynamics as a function of the IR and FPT parameters including chaotic fields. A frequency-resolved profile of dressed molecular states shows that these oscillations are due to interference of many quantum paths analogous to the recently observed control of photoionization of atoms under IR and XUV pulses. By manipulating phases of FPTs we demonstrate an enhancement of molecular dissociation compared to the transform-limited case.

Resolving mechanical effects of light on fluids has fundamental importance with wide applications. Most experiments to date on optofluidic interface deformation exploited radiation forces exerted by normally incident lasers. However, the intriguing effects of photon momentum for any configuration, including the unique total internal reflection regime, where an evanescent wave leaks above the interface, remain largely unexplored. A major difficulty in resolving nanomechanical effects has been the lack of a sensitive detection technique. Here, we devise a simple setup whereby a probe laser produces high-contrast Newton-ring-like fringes from a sessile water drop. The mechanical action of the photon momentum of a pump beam modulates the fringes, thus allowing us to perform a direct noninvasive measurement of a nanometric bulge with sub-5-nm precision. Remarkably, a

We probe the natural complex structures in the transparent insect wings by a simple, non-invasive, real time optical technique using both monochromatic and broadband femtosecond lasers. A stable, reproducible and novel diffraction pattern is observed unveiling long range spatial correlations and structural-symmetry at various length scales for a large variety of wings. While matching the sensitivity of SEM for such microstructures, it is highly efficient for extracting long range structural organization with potentially broad applicability., 5, 4 figures, Conference on Photonics,Optics and Laser Technology 2013

We experimentally and numerically probe the natural quasi-ordered complex structures in the transparent insect wings by a simple, non-invasive, real time optical diffraction technique using monochromatic cw lasers and broadband femtosecond laser pulses. A complex diffraction pattern in transmission unveils the signature of long range spatial correlation in structural arrangement (symmetry) at various length scales on the whole wing surface for a variety of insect wings. A quantitative analysis analysis of the Fast Fourier transform (FFT) angular spectrum reveals a direct link between the structural organization and optical transmitted diffraction patterns. Our findings directly demonstrate how the diffraction pattern through the transparent insect wings is spatially and functionally correlated with its structural origination at various length scales. The methodology of the studies developed in this paper is applicable to a wide class of disordered photonic structures.

A Comment on the Letter by O. Emile and J. Emile, Phys. Rev. Lett. 106, 183904 (2011). The authors of the Letter offer a Reply.

We investigate deformations of fluid interfaces caused by small (∼nN) optical force of a low power laser beam under total-internal-reflection. For air-water interface deformations are undetectable, unlike recently claimed in ref. [3]. Using a critical fluid-fluid interface having weak surface tension large fluid-lens effects in the form of a bump are seen. Our observations support standard optofluidic force-balance with potential for technological applications.

We verify numerically the phenomenon of logical stochastic resonance in a polarization bistable laser. Namely, we show that when one presents two weak binary inputs to the laser system, the response mirrors a logical OR(NOR) output. The reliability of the logic operation is dependent on the noise intensity. As one increases the noise, the probability of the output reflecting the desired OR(NOR) operation increases to nearly unity and then decreases. We also demonstrate that changing the bias morphs the output into another logic operation, AND(NAND), whose probability displays analogous behavior. Furthermore, we highlight the possibility of processing two logic gates in parallel in our laser system by exploiting two coupled orthogonal polarizations that can be detected simultaneously. This suggests that the computational power of the optical system may be enhanced by this additional potential for parallel processing.

We investigate dynamics of atomic and molecular systems exposed to intense, shaped chaotic fields and a weak femtosecond laser pulse theoretically. As a prototype example, the photoionization of a hydrogen atom is considered in detail. The net photoionization undergoes an optimal enhancement when a broadband chaotic field is added to the weak laser pulse. The enhanced ionization is analyzed using time-resolved wavepacket evolution and the population dynamics of the atomic levels. We elucidate the enhancement produced by spectrally-shaped chaotic fields of two different classes, one with a tunable bandwidth and another with a narrow bandwidth centered at the first atomic transition. Motivated by the large bandwidth provided in the high harmonic generation, we also demonstrate the enhancement effect exploiting chaotic fields synthesized from discrete, phase randomized, odd-order and all-order high harmonics of the driving pulse. These findings are generic and can have applications to other atomic and simple molecular systems., 8 pages, 9 figures

Two-color (800 and 400 nm) short (45 fs) linearly polarized pulses are used to ionize and dissociate ${\mathrm{D}}_{2}$ into a neutral deuterium atom and a deuteron. The yields and energies of the ions are measured left and right along the polarization vector. As the relative phase of the two colors is varied, strong yield asymmetries are found in the ion-energy regions traditionally identified as bond softening, above-threshold dissociation and rescattering. The asymmetries in these regions are quite different. A model based on the dynamic coupling by the laser field of the gerade and ungerade states in the molecular ion accounts for many of the observed features.

We investigate the dynamics of diatomic molecules subjected to both a femtosecond mid-infrared laser pulse and Gaussian white noise. The stochastic Schr\"odinger equation with a Morse potential is used to describe the molecular vibrations under noise and the laser pulse. For weak laser intensity, well below the dissociation threshold, it is shown that one can find an optimum amount of noise that leads to a dramatic enhancement of the dissociation probability. The enhancement landscape which is shown as a function of both the noise and the laser strength, exhibits a global maximum. A frequency-resolved gain profile is recorded with a pump-probe set-up which is experimentally realizable. With this profile we identify the linear and nonlinear multiphoton processes created by the interplay between laser and noise and assess their relative contribution to the dissociation enhancement., Comment: 5 pages,5 figures

We experimentally probe the structural organization of complex bio-photonic architecture on transparent insect wings by a simple, non-invasive, real-time optical technique. A stable and reproducible far-field diffraction pattern in transmission was observed using collimated cw and broadband fs laser pulses. A quantitative analysis of the observed diffraction pattern unveiled long-range quasi-periodic order in the arrangement of the microstructures over mm scale. These observations agree well with the Fourier analysis of SEM images of the wing taken at various length scales. We propose a simple quantitative model based on optical diffraction by an array of non overlapping microstructures with minimal disorder which supports our experimental observations. We observed a rotation of the original diffraction profile by scanning the laser beam across the wing sample which gives direct signature of organizational symmetry in microstructure arrangements at various length scales. In addition, we report the first optical detection of reorganization in the photonic architecture on the Drosophila wings by various genetic mutations. These results have potential for the design and development of diffractive optical components for applied photonics and may open up new opportunities in biomimetic device research.

We show experimentally that optical two-dimensional systems such as vectorial lasers can exhibit novel stochastic resonances. All optical noise and modulation of this system allows the isolation of so-called inhibitional and rotational stochastic resonances. In particular, incoherent rotational tunneling is shown to be sensitive enough to be also induced by Faraday noise and by quantum noise, i.e., external spontaneous emission.

Attosecond science has opened up the possibility of manipulating electrons on their fundamental timescales. Here, we use both theory and experi- ment to investigate ionization dynamics in helium on the attosecond timescale by simultaneously irradiating the atom with a soft x-ray attosecond pulse train (APT) and an ultrafast laser pulse. Because the APT has resolution in both energy and time, we observe processes that could not be observed without resolu- tion in both domains simultaneously. We show that resonant absorption is impor- tant in the excitation of helium and that small changes in energies of harmonics that comprise the APT can result in large changes in the ionization process. With the help of theory, ionization pathways for the infrared-assisted excitation and ionization of helium by extreme ultraviolet (XUV) attosecond pulses have been identified and simple model interpretations have been developed that should be of general applicability to more complex systems (Zewail A 2000 J. Phys. Chem. A 104 5660-94).

We have used few-cycle IR and EUV laser pulses in pump-probe arrangement to trace out the dissociation pathways in CO when exploded by strong laser fields. We present two preliminary sets of data of different pump pulses. In these sets, different excited state of CO cations are populated using (< 10 fs) IR, and EUV pulses respectively. We followed the time evolution of these states using the time-resolved Coulomb explosion imaging technique. We compare the time evolution of IR- and EUV-induced excited states by measuring the KER of the fragment ions as a function of the time delay between the pump and the IR probe pulse.

We demonstrate an experimental control of electron localization in the deuterium molecular ion created and dissociated by the combined action of an attosecond pulse train (APT) and a femtosecond IR laser pulse. A left-right asymmetric ejection of the deuterium ions, characterized by an asymmetry parameter A, exhibits oscillations with a full laser period when the time-delay between the APT and IR pulses is scanned with 300as resolution.