UV-VIS absorption spectroscopy of large molecules for applications in matter wave interferometry

We study the optical properties of various large molecules with respect to their suitability for new matter wave interference and detection schemes. Optical phase gratings for molecules will only be compatible with a sufficiently small absorption cross section visible while optical detection schemes may exploit strong UV resonances. We compare UV-VIS spectra of various biomolecules, such as amino acids, polypeptides, and proteins, with those of new perfluoroalkylated molecules and carbon nanotubes, and we discuss their suitability for coherent matter wave experiments.     

On the prospects of interferometry and deflectometry for characterizing large molecules

We investigate the prospects of near-field matter-wave interferometry for the sensitive determination of molecular properties, such as electric polarizabilities, electric and magnetic dipole moments or even life-times of some molecular states. We discuss how important principles of our present quantum experiments can be transferred to the classical regime, i.e. to a Moiré deflectometer in order to also measure characteristic properties of large clusters and biomolecules.     

Algorithm for near-field reconstruction based on radial-shearing interferometry

A new iterative algorithm to be used to precisely reconstruct near-field distribution from an interferogram of a laser output generated by a cyclic radial-shearing interferometer is proposed. First, by use of a window function around the zero-frequency part of the Fourier transform of the interferogram and calculation of the inverse Fourier transform of the zero-frequency part, we obtain the background intensity distribution of the interferogram. Then, according to the iterative algorithm, the near-field distribution of the laser output is precisely reconstructed from the background intensity distribution obtained in the first step. A numerical simulation and an actual experiment of the near-field reconstruction of the laser output with arbitrary amplitude distribution are implemented successfully.     

Structure of clusters of pentacene molecules and their polarizabilities

We calculate and compare the ground state structures of one, two and three pentacene molecule clusters, using B3LYP and B97-D density functionals, and polarizabilities in the ground state structure to examine the extent of anisotropy for applications in electronic device fabrication. B3LYP and B97-D functionals perform sufficiently well for a single pentacene molecule, but for two and three molecule clusters, the inclusion of dispersive interactions through B97-D becomes necessary. For two and three molecule clusters the energy landscape near ground state is flat in molecular coordinates, implying multiple related structures may be accessible at room temperature. Further, for the ground state structures, the polarizability along the long axis of the molecule is larger than the other two directions. This may make it possible to explain the beneficial effect of applying an electric field during processing of pentacene films in electronic devices, as observed experimentally; specifically, in this context, the structural and polarizability data presented could allow for development of models for nucleation and growth of pentacene films.     

Optical coherence pulsed interferometry: shaping probe pulses in time-domain interferometry

The autocorrelation of a modulated coherent light source is used as a probe pulse in a time-domain interferometry scheme. With respect to conventional techniques, higher flexibility in selecting the shape of the probe pulse can be achieved by simply acting on the modulation parameters. The complex amplitude of short pulses propagating through a generic optical device can be directly measured, with no need for fast sampling and time synchronization. The potentialities of the technique are shown by reporting measurements of amplitude distortion, group delay, and frequency chirp of optical pulses transmitted through integrated ring resonators.     

Optical interferometry in phase separated He---He mixture films

We report on interferometric studies of ³He---⁴He liquid mixtures. Anomalous wetting phenomena were observed in phase separated mixture films: the upper ³He-rich phase did not wet the lower ⁴He-rich phase under a small continuous feed of ⁴He atoms to the vapor phase. Instead, under this dynamic situation, floating pools of the ³He-rich phase were stabilized with a contact angle on the order of 10 mrad. In equilibrium, the concentrated ³He-rich phase was found to nucleate uniformly on the free surface, consistent with Antonow's rule.     

Optical pulsation mechanism based on optical near-field interactions

We theoretically demonstrate optical pulsation based on optical near-field interactions between quantum nanostructures. It is composed of two quantum dot systems, each of which consists of a combination of smaller and larger quantum dots, so that optical excitation transfer occurs. With an architecture in which the two systems take the role of a timing delay and frequency up-conversion, we observe pulsation in populations pumped by continuous-wave light irradiation. The pulsation is induced with suitable setting of parameters associated with the optical near-field interactions. This will provide critical insights toward the design and implementation of experimental nanophotonic pulse generating devices.     

两步广义相移干涉术的光学实验验证

提出了一种基于两步广义相移干涉术的波前再现技术以及基于衍射场统计特性的未知相移值提取算法,并且进行了光学实验验证.该方法中可仅利用两幅干涉图及一次不需精确预设的未知相移,参照物光光强和参考光光强,即可通过计算提取真实的相移量,进而恢复出物波波前复振幅,而无需借助傅里叶谱分析或数字滤波等操作.在光学实验中,对借助于空间光调制器（SLM）的间接输入和三维漫反射物体直接输入两种情况进行了详细地研究,得到的光学实验结果验证了所提方案的有效性和可行性. 关键词： 信息光学 相移干涉术 波前再现 数字图像处理     

Holographic interferometry for testing large phase objects

The class of sulphonated triazinyl-stilbene compounds was systematically investigated for its application in N₂-laser-pumped dye lasers. All tested dyes had good lasing-characteristics in methanolic and aqueous solutions. Many of these dyes, all lasing in the violet and blue spectral region, were demonstrated to be superior to other common dyes that are normally soluble in organic solvents, only. Broad tuning ranges, high stability and good efficiencies were found.     

Optical distance sensing using digital speckle shearing interferometry

A novel distance sensing technique using digital speckle shearing interferometry is outlined in this paper. The primary incentive for the development of this technique is of one that can be: (i) incorporated into any TV imaging system; (ii) used as a focusing mechanism; (iii) suited to measure from diffuse targets; and (iv) relatively insensitive towards the environment. Results obtained reveal the feasibility of further research and development of this technique for practical applications.     

Optical interferometry for measurement of Rayleigh and dilatational waves

Two-beam optical interferometry provides a highly sensitive new technique for the measurement of both Rayleigh waves and dilatational waves. A new optical arrangement overcomes previous objections to interferometry by its differential nature. The acoustically perturbed surface need not be exceptionally flat and the specimen need not be exactly aligned. The technique can be used to measure the phase and amplitude of Rayleigh waves to within a fraction of a wavelength from a discontinuity on any fully or partly reflecting surface. Dilatational waves are measureable in any transparent medium.     

Optical near-field mapping of bright and dark quantum dot states

We theoretically investigate scanning near-field optical microscopy (SNOM) of semiconductor quantum dots. A general theoretical framework is developed that accounts for photo excitation and relaxation in complex dielectric environments. We find that in the near-field regime bright and dark excitonic states become mixed, opening new channels for the coupling to the electromagnetic field.     

Optical encryption using phase-shifting interferometry in a joint transform correlator

We propose an optical encryption technique where the encrypted field and the decrypting key are obtained by three-step phase-shifting interferometry and registered as digital Fresnel holograms in a joint transform correlator architecture. Decryption can be achieved by digital or optical means. The technique allows the complete process to be achieved at high speed and data to be transfered via digital communication channels. Experimental implementation is performed in a system based on a programmable liquid-crystal TV display working in pure phase mode to represent the input data and to introduce the required phase shifts. A CCD is used to register the output data.     

Scanning near-field optical coherent spectroscopy of single molecules at 1.4 K

We present scanning near-field extinction spectra of single molecules embedded in a solid matrix. By varying the tip-molecule separation, we modify the line shape of the spectra, demonstrating the coherent nature of the interaction between the incident laser light and the excited state of the molecule. We compare the measured data with the outcome of numerical calculations and find a very good agreement.     

Optical stark decelerator for molecules

We demonstrate a single stage optical Stark decelerator for neutral molecules which is capable of reducing the translational energy of benzene molecules within a molecular beam by 15% in a single pulsed Gaussian optical field of 15 ns duration. The change in velocity induced by the optical potential is measured by the change in the time of flight of benzene molecules ionized by a second optical field after the slowing field is turned off. A maximum reduction in the velocity of 25 m/s was measured using a single Gaussian beam with a peak intensity of 1.6 x 10(12) W/cm(2) corresponding to a maximum well depth of 253 K.     

Optical production of ultracold polar molecules

We demonstrate the production of ultracold polar RbCs molecules in their vibronic ground state, via photoassociation of laser-cooled atoms followed by a laser-stimulated state transfer process. The resulting sample of X1Sigma+ (nu = 0) molecules has a translational temperature of approximately 100 microK and a narrow distribution of rotational states. With the method described here it should be possible to produce samples even colder in all degrees of freedom, as well as other bialkali species.