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An intensity pump femtosecond (fs) pulse incident into a transparent medium will produce filamentation and accompany supercontinuum (SC) spectrum generation. The polarization of the SC spectrum is always parallel to that of the pump pulse. How to control the polarization of the SC spectrum is a very interesting and crucial issue due to its great potential applications in remote sensing and time-resolved spectroscopy. Here we present a method to control the polarization of the SC spectrum generated in an optical isotropic medium, based on the nonlinear interaction between the two pump pulses with different linear polarizations. During the fs pulse filamentation, the optical Kerr effect induces ultrafast birefringence in the optical isotropic medium, which leads to different refractive indices in the two orthogonal directions parallel and perpendicular to the incident polarization, and hence, the resulting relative phase difference changes the polarizations of the pump pulses. The polarization states of both the pump pulses and the SC spectra can be achieved by changing the angle between the polarization directions of the two pulses. We unveil the mechanism of the polarization changes of the pump pulses and the SC spectra.

Engineering the diversity of the spatial structure of polarization states offers a new approach to produce controllable and designable filament patterns. Here we predict theoretically and demonstrate experimentally the novel collapsing behaviors of the optical fields by using the elliptical symmetry hybrid polarization structure in a self-focusing Kerr medium. The results reveal that the distribution of the hybrid polarization states, the spin angular momentum (SAM) gradient, and the collapsing patterns could be manipulated by changing the eccentricity, the topological charge, and the initial phase of the optical field. Owing to the synergy of the hybrid polarization states and its spatial symmetry, the collapsing behaviors are controllable, and have the robust feature insensitive to the random noise. Our idea may offer an alternative route to produce the controllable and robust multiple filamentation in other nonlinear systems, thereby facilitating the development of additional surprising applications.

We present a two-photon interference experiment in a modified Mach-Zehnder (MZ) interferometer in which two Hong–Ou–Mandel effects occur in tandem and construct superposed two-photon states. The signal photons pass both the arms of the MZ interferometer while the idler photons pass one arm only. Interestingly, the probability of the idler photons emerging from any output port still shows a sine oscillation with the two-photon phase difference and it can be characterized only by the indistinguishability of the two-photon amplitudes. We also observe a two-photon interference pattern with a period being equal to the wavelength of the parametric photons instead of the two-photon photonic de Broglie wavelength due to the presence of two-photon phase difference, in particular, with complementary probabilities of finding the two-photon pairs in two output ports. The abundant observations can facilitate a more comprehensive understanding of the two-photon interference.

We present an inverse method to engineer uniform-intensity focal fields with arbitrary shape. Amplitude, phase, and polarization states, as adjustable parameters, are used to seek the desired focal fields in the non-iterative computational procedure. Our method can be applied to the cases with low and moderate numerical aperture (NA), in which case the feasibility and validity of our approach have been demonstrated in theory, simulation and experiment, respectively. For the case of higher NA, simulated results based on the Richards-Wolf diffraction integral are shown. We also made some discussions on the experiments with the higher NA. Our method should have wide applications in optical micro machining, optical trapping and so on.

We present an optical encryption approach based on the combination of fractal Fresnel lens (FFL) and fractional Fourier transform (FrFT). Our encryption approach is in fact a four-fold encryption scheme, including the random phase encoding produced by the Gerchberg–Saxton algorithm, a FFL, and two FrFTs. A FFL is composed of a Sierpinski carpet fractal plate and a Fresnel zone plate. In our encryption approach, the security is enhanced due to the more expandable key spaces and the use of FFL overcomes the alignment problem of the optical axis in optical system. Only using the perfectly matched parameters of the FFL and the FrFT, the plaintext can be recovered well. We present an image encryption algorithm that from the ciphertext we can get two original images by the FrFT with two different phase distribution keys, obtained by performing 100 iterations between the two plaintext and ciphertext, respectively. We test the sensitivity of our approach to various parameters such as the wavelength of light, the focal length of FFL, and the fractional orders of FrFT. Our approach can resist various attacks.

We introduce a general fractal lattice growth model, significantly expanding the application scope of the fractal in the realm of optics. This model can be applied to construct various kinds of fractal "lattices" and then to achieve the design of a great diversity of fractal vector optical fields (F-VOFs) combinating with various "bases". We also experimentally generate the F-VOFs and explore their universal focusing behaviors. Multiple focal spots can be flexibly enginnered, and the optical tweezers experiment validates the simulated tight focusing fields, which means that this model allows the diversity of the focal patterns to flexibly trap and manipulate micrometer-sized particles. Furthermore, the recovery performance of the F-VOFs is also studied when the input fields and spatial frequency spectrum are obstructed, and the results confirm the robustness of the F-VOFs in both focusing and imaging processes, which is very useful in information transmission.

Polarizer, as an indispensable optical element, has been widely used in various optical systems, which splits a beam into two beams of orthogonal linear polarizations. Due to the appearance of the vector optical field (VOF) and its unique properties, the vector polarizer also meets the requirement in a wide variety of applications. Here we present and demonstrate the realization of dielectric broadband vector polarizer, being in fact a liquid-crystal-based space-variant uniaxial crystal (LC-SV-UAC), which is made by a wedged thin cell adhered with space-variant photo-aligned dichroic dye films and filled with the nematic liquid crystal with a thickness of tens of microns. The vector polarizer works based on the birefringent mechanism to spatially separate the orthogonally polarized ordinary and extraordinary beams. The vector polarizers via a LC-SV-UAC have the advantages of mass-production and easy fabrication of large-size and complex structures. In particular, the high-performance broadband vector polarizers we presented and fabricated can not only flexibly tailor the polarization structures and the intensity patterns of optical fields but also act as a high-efficiency generator of VOF, and a key element for realizing the VOF laser and for fabricating the novel photon states in the future.

Based on the nonlinear polarization rotation (NPR) technique and a fiber Mach–Zehnder interferometer (MZI), a fiber laser which can work in two different modes has been demonstrated. In one mode, it works as a continuous wave (CW) multiwavelength laser, and stable dual-, triple- and tetra-wavelength lasing with the wavelength spacing of 1.1 nm are obtained. In the other mode, it works as a passively mode-locked fiber laser, and the generated pulses have a repetition rate of 10.6 MHz, an FWHM width of 800 ps and the largest energy of 1 nJ. The multi-functional property makes this fiber laser a very convenient, cost effective and multi-purpose laser source.

We present a generalized Poincar\'e sphere (G sphere) and generalized Stokes parameters (G parameters), as a geometric representation, which unifies the descriptors of a variety of vector fields. Unlike the standard Poincar\'e sphere, the radial dimension in the G sphere is not used to describe the partially polarized field. The G sphere is constructed by extending the basic Jones vector basis to the general vector basis with the continuously changeable ellipticity (spin angular momentum, SAM) and the higher dimensional orbital angular momentum (OAM). The north and south poles of different spherical shell in the G sphere represent the pair of different orthogonal vector basis with different ellipticity (SAM) and the opposite OAM. The higher-order Poincar\'e spheres are just the two special spherical shells of the G sphere. We present a quite flexible scheme, which can generate all the vector fields described in the G sphere. The salient properties of this representation are able to treat the complicated geometric phase of arbitrary vector fields in the future.

The redistribution of the energy flow of tightly focused ellipticity-variant vector optical fields is presented. We theoretically design and experimentally generate this kind of ellipticity-variant vector optical field, and further explore the redistribution of the energy flow in the focal plane by designing different phase masks, including fanlike phase masks and vortex phase masks, on them. The flexibly controlled transverse energy flow rings of the tightly focused ellipticity-variant vector optical fields with and without phase masks can be used to transport multiple absorptive particles along certain paths, which may be widely applied in optical trapping and manipulation.

The scheme for generating vector optical fields should have not only high efficiency but also flexibility for satisfying the requirements of various applications. However, in general, high efficiency and flexibility are not compatible. Here we present and experimentally demonstrate a solution to directly, flexibly, and efficiently generate vector vortex optical fields (VVOFs) with a reflective phase-only liquid crystal spatial light modulator (LC-SLM) based on optical birefringence of liquid crystal molecules. To generate the VVOFs, this approach needs in principle only a half-wave plate, an LC-SLM, and a quarter-wave plate. This approach has some advantages, including a simple experimental setup, good flexibility, and high efficiency, making the approach very promising in some applications when higher power is need. This approach has a generation efficiency of 44.0%, which is much higher than the 1.1% of the common path interferometric approach.

In traditional ghost imaging, the entangled photon pairs produced from the spontaneous parametric down conversion (SPDC) process are used. There is an intrinsic disadvantage that the utilization efficiency of the photon pairs is very low. Inasmuch as all the correlated photon pairs produced by the degenerate SPDC process can be used to record the image of an object, the ghost imaging scheme we present here has a higher utilization efficiency of the photon pairs. We also investigate the robustness of our experimental scheme. The experimental results show that, no matter whether the photon-pair source is two light cones or two beam-like spots, the clear image of the object can be obtained. The slight rotation of the nonlinear crystal has no influence on the imaging quality. Our experimental results also demonstrate that when the part of the photon-pair source in the signal path or the idler path is blocked by unwanted things, the clear ghost image of the object can still be recorded.

We investigate a novel spatial geometric phase of hybrid-polarized vector fields consisting of linear, elliptical and circular polarizations by Young's two-slit interferometer instead of the widely used Mach–Zehnder interferometer. This spatial geometric phase can be manipulated by engineering the spatial configuration of hybrid polarizations, and is directly related to the topological charge, the local states of polarization and the rotational symmetry of hybrid-polarized vector optical fields. The unique feature of geometric phase has implications in quantum information science as well as other physical systems such as electron vortex beams.

Transporting information is one of the important functions of photons and is also the essential duty of information science. Here, we realize multiple imaging by detecting photons with changeable wavelengths based on time-resolved correlation measurements. In our system, information from multiple objects can be transported. During this process, the wavelength of the photons illuminating the objects is different from the wavelength of the photons detected by the detectors. More importantly, the wavelength of the photons that are utilized to record images can also be changed to match the sensitive range of the used detectors. In our experiment, images of the objects are reconstructed clearly by detecting the photons at wavelengths of 650, 810, and 1064 nm, respectively. These properties should have potential applications in information science.

We propose a method to generate the phase-conjugate wave of the vector field by degenerate four-wave mixing in a c-cut Fe-doped LiNbO3 crystal. We demonstrate experimentally that the phase-conjugate wave of the vector field can be generated. In particular, the phase-conjugate vector field has also the peculiar function of compensating the polarization distortion, as the traditional phase-conjugate scaler field can compensate the phase distortion.

We propose a flexible method to record and reconstruct vector fields with space-variant polarization distribution in c-cut Fe-doped LiNbO3, based on photorefractive two-wave mixing. To our knowledge, this is the first approach for the reconstruction of vector fields without using the photoinduced anisotropy of the recording material.

We present theoretically and generate experimentally a vector optical field with parabolic symmetry of linear polarization. We extend the study to the modified parabolic-symmetry vector fields. We explore their tightly focusing behaviors, in particular, a modified parabolic-symmetry vector field can be tightly focused into a high-performance subwavelength sharp line.

We numerically and experimentally explored generation and regulation of subwavelength multiple focal spots produced by tight focusing patterned vector optical fields (PVOFs). We presented a modified Richard-Wolf diffraction integration method suitable for the tight focusing of the PVOFs. By tailoring the spatial geometry and the polarization distributions of the PVOFs, simulations show that the diverse spatial configurations of subwavelength multiple focal spots can be achieved. To verify our idea, we experimentally generated the theoretically calculated examples of femtosecond PVOFs, then tightly focused them on the surface of the crystalline silicon wafers, and finally characterized the morphologies of modified surfaces. The SEM (scanning electronic microscopy) images confirmed that the experimental results are in good agreement with the simulations. Based on the diverse controlling degrees of freedom of PVOFs, the resultant subwavelength focal fields are flexible and powerful in parallel processing, optical manipulation and so on.

The Heisenberg uncertainty principle suggests that it is impossible to determine the trajectory of a quantum particle in the same way as a classical particle. However, we may still yield insight into novel behavior of photons based on the average photon trajectories (APTs). Here we explore the APTs of optical fields carrying spin angular momentum (SAM) and orbital angular momentum (OAM) under the paraxial condition. We define the helicity and differential helicity for unveiling the three-dimensional spiral structures of the APTs of optical fields carrying the SAM and/or the OAM. We clarify the novel behaviors of the APTs caused by the SAM and OAM as well as the SAM-OAM coupling. The APT concept is also very helpful for profoundly understanding trapped particle motion and has the potential to elucidate other physical systems. Due to the presence of the helical path caused by the SAM and/or the OAM, the actual traveling distance of the photons might be much longer than the geometric distance.

We present a scheme for realizing femtosecond multi-filamentation with designable quantity and locations of filaments, based on the control of multi-focal spots formed by patterned optical fields (POFs) composed of multiple individual optical fields (IOFs). A computer-controlled spatial light modulator is used to engineer the POFs. In particular, we introduce a blazed phase grating in any IOF, which increases a degree of freedom, making the engineering of multi-focal spots becomes more flexible. We achieve experimentally the aim controlling femtosecond multi-filamentation in a K9 glass. Our scheme has great flexibility and convenience in controlling the multi-filamentation in quantity and locations of filaments and strength of interaction between filaments.

We proposed and demonstrated a room-temperature multiwavelength Yb-doped fiber ring laser with high stability based on a Mach-Zehnder interferometer by exploiting spatial hole burning and polarization hole burning effects, from which stable eight lasing wavelengths is obtained. The number of the lasing wavelengths (eight) is the most to our knowledge, and the wavelength spacing is 1.1 nm. Triple-, and dual-wavelength operation with the wavelength spacing of 1.1 nm or its integral multiples have been obtained by adjusting the intracavity polarization controllers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 723–725, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23206

We focus on a new kind of vector optical field with bipolar symmetry of linear polarization instead of cylindrical and elliptical symmetries, enriching members of family of vector optical fields. We design theoretically and generate experimentally the demanded vector optical fields and then explore some novel tightly focusing properties. The geometric configurations of states of polarization provide additional degrees of freedom assisting in engineering the field distribution at the focus to the specific applications such as lithography, optical trapping, and material processing.

We propose a convenient approach for managing orbital angular momentum (OAM) of second-harmonic photons generated by a quadratic nonlinear interaction under noncolinear type-I phase matching condition. Since the OAMs of two fundamental photons can be flexibly controlled by using computer-generated holograms, we were able to realize arbitrary combination of both OAMs and experimentally confirm the OAM conservation selection rule ${\ensuremath{\ell}}_{2\ensuremath{\omega}}={\ensuremath{\ell}}_{\ensuremath{\omega}}^{\ensuremath{'}}+{\ensuremath{\ell}}_{\ensuremath{\omega}}^{\ensuremath{'}\ensuremath{'}}$ in general cases. In particular, our approach could be used to generate the second-harmonic photon states with fractional and odd-order OAMs.

We propose an approach for the optical encryption of ghost images reconstructed from the spatially correlated classical two-beam pairs. This approach has the capability of encrypting ghost images by flexibly manipulating the position correlation of a pair of ``signal'' and ``idler'' beams. We experimentally demonstrate that the perfect ghost image can be extracted by decrypting the encrypted information of an object, in particular, our approach under eavesdropping has a higher security for encryption compared with previous approaches.

Two-dimensional near-wavelength microstructures have been fabricated on a copper film and a silicon wafer by femtosecond vector optical fields with different spatial polarization distribution, at a central wavelength of 800 nm, pulse duration of ∼70 fs, and a repetition rate of 1 kHz. Laser-induced ripples appear at the ablated region on silicon when the laser fluence is above the ablated threshold. When the number of the irradiated pulses increases, ripples with interspace larger than the wavelength could be observed, while the dimension of the ablated region has a slight variation. In the induced microstructures on a copper film, the microstructures in a ring have been observed under the irradiation of a few pulses. Under the irradiation of the multipulse femtosecond vector field, differently from the condition of the silicon, the induced microstructures on the metallic copper surface exhibit the anisotropic extending feature dependent on the polarization distribution of the vector field. The physics behind this unique feature is the anisotropic excitation and propagation of surface plasmon, caused by the coupling of the subsequent irradiation pulses with the existing microstructure. In this case, the surface plasmons resonance in the induced 2D microstructures is closely related to the induced grating structures on the surface.

We present and demonstrate an approach for femtosecond laser processing by using patterned vector optical fields (PVOFs) composed of multiple individual vector optical fields. The PVOFs can be flexibly engineered due to the diversity of individual vector optical fields in spatial arrangement and distribution of states of polarization, and it is easily created with the aid of a spatial light modulator. The focused PVOFs will certainly result in various interference patterns, which are then used to fabricate multi-microholes with various patterns on silicon. The present approach can be expanded to fabricate three-dimensional microstructures based on two-photon polymerization.

Femtosecond laser filamentation is generally initialized from unpredictable symmetry breaking caused by random noise, causing it to be barely controlled. However, it is always anticipated for stable and controllable filamentation. We present and demonstrate the idea that hybridly polarized vector fields with axial symmetry broken polarization, associated with a pair of orthogonally linearly polarized vortices carrying the opposite-handed orbital angular momenta, could achieve controllable and robust multiple filamentation. Here, our motivation is to unveil the underlying physics behind such controllable and robust multiple filamentation. The symmetry breaking should first be actively controllable and then be able to effectively inhibit random noise. Robust multiple filamentation is inseparable from the fact that the phases between the multiple filaments are always locked. In contrast, uncontrollable multiple filamentation is always accompanied with loss of phase, i.e., the multiple filaments become incoherent to each other. Our results may offer a suggestion for achieving controllable and robust multiple filamentation in other systems.

We experimentally demonstrate a novel ghost imaging experiment utilizing a classical light source, capable of resolving objects with a high visibility. The experimental results show that our scheme can indeed realize ghost imaging with high visibility for a relatively complicated object composed of three near-ellipse-shaped holes with different dimensions. In our experiment, the largest hole is ~36 times of the smallest one in area. Each of the three holes exhibits high-visibility in excess of 80%. The high visibility and high spatial-resolution advantages of this technique could have applications in remote sensing.

Field collapse, which occurs in various nonlinear systems, has attracted much attention, owing to its universality, complexity, and applicability. A great challenge and expectation is to achieve the controllable and designable collapsing pattern. Here we predict theoretically and demonstrate experimentally the novel collapsing behaviors of the vector optical fields in a self-focusing Kerr medium. Surprisingly, the results reveal that the collapse of the vector optical field is controllable and designable by engineering the distribution of hybrid states of polarization, and has the robust feature insensitive to the random noise. Our idea has its significance which it opens a new window for manipulating the optical field and the different kinds of field, and then facilitates to push the related researches.

We present in this Letter the second-harmonic generation of femtosecond pulses in double-line-written waveguides fabricated in periodically poled lithium niobate (PPLN) with femtosecond laser pulses. In a 10-mm-long sample, a normalized conversion efficiency of 12.6% W(-1) cm(-2) has been achieved for 40 fs pump pulses with the wavelengths centered at 1550 nm. Simulation results show that in PPLN waveguides the FWHM of wavelength tuning curve for 40 fs pump pulses is 42 nm, which is 15 times of that for 40 ps pump pulses.

Second harmonic generation of femtosecond pulses in PPLN waveguide written by femtosecond laser pulses was described both theoretically and experimentally. An average power conversion efficiency of 21.5% was obtained.

In this paper, a novel Q-switched fiber laser made up of OptoCeramic electrooptic ceramics is reported. The ring laser is composed with an electrooptic ceramics modulator as Q-switched, a highly Yb-doped fiber as the gain medium, and pumped by a semiconductor laser of 976 nm wavelength. Q-switched is realized from modulating the loss, controlled by the material refractive index, which is changed with the voltage of OptoCeramic element. The laser system generates pulses about 100ns, with the repetition rate continuously adjusted from 3kHz to more than 40 kHz.

The numerical study of annealed proton exchanged (APE) waveguide in Z-cut periodically poled LiNbO 3 is presented using finite element method (FEM), compared with beam propagation method (BPM). Also given the analysis of the effects of different annealed time and annealed temperature on modes distribution.

A dual-wavelength narrow line width laser system, with ultra-narrow wavelength spacing, is proposed and demonstrated. The operation principle of the laser system is based on the pumped-induced thermal effects of the Er-Yb-doped fiber DBR laser. We designed and constructed a common Er-Yb-doped DBR fiber laser with proper parameters. With the pump power of the DBR laser increasing, the Bragg wavelengths and the bandwidths of the two gratings will change unequally. When pumped with 45mW, we obtain a stable dual wavelength lasing with the bandwidth of 0.014nm and the wavelength spacing of 0.055nm.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Self similar mode locked fiber laser is studied based on a numerical model. By introducing a dimensionless factor k to characterize the pulse, the self similar pulse formation and its temporal and spectral changes are investigated throughout the cavity. The influences of all the elements inside the cavity on the pulse formation are also studied.

In an intermediate asymptotic propagation distance, pulse's self similar evolution is influenced by the initial pulse width and chirp, as a result pulses can not completely evolve into a parabolic pulse, which can affect the compression of the evolved pulse. The self similar evolution results of ultra-short pulse with different width and initial chirp coefficient are studied by numerical simulation. The study shows the wider the pulse is, the worse the self similar evolution and compression are; it also shows the initial chirp can greatly hold out the self similar evolution and compression, the larger the chirp and the wider the pulse, the worse the self similar evolution, and the influence of the positive chirp on the evolution is bigger than that of negative chirp.

We present a modified, more universal scheme for generating vector fields. Here we design in principle and experimentally generate a new kind of uniformly elliptically polarized vector field, which has the same ellipticity and sense of local elliptic polarization at any location and also has a flexibly designable distribution of orientation of the elliptic polarization. An introduced additional degree of freedom is used to flexibly change the ellipticity. In particular, the ellipticity and the orientation of polarization can be independently controlled by two parameters. This makes it easier to both control the spatial structure of the polarization and to engineer the focusing field.

We develop analytical formulae for describing the tight focusing field of the Laguerre–Gaussian vector field with space-variant distribution of states of polarization in the frame of the Rayleigh–Sommerfeld theory. The analytical formulae of three radial, azimuthal and longitudinal components are very beneficial in order to understand the tightly focused field. This result is of great importance to improving the design and engineering the tightly focused field, by using phase and polarization, for applications such as optical tweezers and optical manipulation. This method is also applicable to the homogeneously polarized optical fields and optical vortex fields. In particular, these analytical formulae can also describe the dynamic process of the tightly focused fields, for example, average photon trajectories.

We present in principle and demonstrate experimentally a new kind of vector fields: elliptic-symmetry vector optical fields. This is a significant development in vector fields, as this breaks the cylindrical symmetry and enriches the family of vector fields. Due to the presence of an additional degrees of freedom, which is the interval between the foci in the elliptic coordinate system, the elliptic-symmetry vector fields are more flexible than the cylindrical vector fields for controlling the spatial structure of polarization and for engineering the focusing fields. The elliptic-symmetry vector fields can find many specific applications from optical trapping to optical machining and so on.

We propose an approach to enhance the security of optical encryption based on double-random phase encryption in a 4f system. The phase key in the input plane of the 4f system is generated by the Yang–Gu algorithm to control the phase of the encrypted information in the output plane of the 4f system, until the phase in the output plane converges to a predesigned distribution. Only the amplitude of the encrypted information must be recorded as a ciphertext. The information, which needs to be transmitted, is greatly reduced. We can decrypt the ciphertext with the aid of the predesigned phase distribution and the phase key in the Fourier plane. Our approach can resist various attacks.

We propose a flexible method to record and reconstruct vector fields with space-variant polarization distribution in c-cut Fe-doped LiNbO3, based on photorefractive two-wave mixing. To our knowledge, this is the first approach for the reconstruction of vector fields without using the photoinduced anisotropy of the recording material.

We present a convenient, efficient, and robust scheme for controlling the states of polarization and then generating vector fields using a closed-loop Sagnac interferometric configuration. A geometric phase introduced by the wave plates is used to control the phase shift between the two counterpropagating orthogonally linearly polarized fields. A space-variant phase plate substitutes for a spatial light modulator as a space-variant phase device. We have demonstrated experimentally that this scheme has an efficiency beyond 83% converting the input traditional linearly polarized laser into the vector fields. This scheme should also be efficient and reliable for creating the ultrashort-pulsed, high-power, and single-photon vector sources.

We present, design and generate a new kind of vector optical fields with linear polarization distributions modeling to electric and magnetic field lines. The geometric configurations of "electric charges" and "magnetic charges" can engineer the spatial structure and symmetry of polarizations of vector optical field, providing additional degrees of freedom assisting in controlling the field symmetry at the focus and allowing engineering of the field distribution at the focus to the specific applications.

Two-dimensional near-wavelength microstructures have been fabricated on copper film by femtosecond vector optical fields with different spatial polarization distribution, at a central wavelength of 800 nm, a pulse duration of ∼70 fs, and a repetition rate of 1 kHz. In the induced microstructures, fine structures with interperpendicular orientations have been observed under the irradiation of a few pulses. Under the irradiation of the multipulse femtosecond vector field, differently from on the dielectric and semiconductor surfaces, the induced microstructures on the metallic copper surface exhibit an anisotropic extending feature dependent on the polarization distribution of the vector field. The physics behind this unique feature are the anisotropic excitation and propagation of surface plasmons, caused by the coupling of the subsequent irradiation pulses with the existing microstructure.

We explore the peculiar interference behaviors of the vector fields in the Young's two-slit configuration. The interference patterns have a chessboard structure in the middle region and depend on the topological charge and the initial phase of the input vector field. The results have potential applications such as characterizing the topological properties of the arbitrary vector fields.

We have fabricated the complicated two-dimensional subwave-length microstructures induced by the femtosecond vector light fields on silicon. The fabricated microstructures have the interval between two ripples in microstructures to be around 670-690 nm and the depth of the grooves to be about 300 nm when the pulse fluence of 0.26 J/cm2 is slightly higher than the ablated threshold of 0.2 J/cm2 for silicon under the irradiation of 100 pulses. The ripples are always perpendicular to the direction of the locally linear polarization. The designable spatial structure of polarization of the femtosecond vector light field can be used to manipulate the fabricated microstructure.