Search results for "Optical axis"
showing 10 items of 34 documents
Bifractal focusing and imaging properties of Thue-Morse Zone Plates.
2015
We present a new family of Zone Plates (ZPs) designed using the Thue-Morse sequence. The focusing and imaging properties of these aperiodic diffractive lenses coined Thue-Morse Zone Plates (TMZPs) are examined. It is demonstrated that TMZPs produce a pair of self-similar and equally intense foci along the optical axis. As a consequence of this property, under broadband illumination, a TMZP produces two foci with an extended depth of focus and a strong reduction of the chromatic aberration compared with conventional periodic ZPs. This distinctive optical characteristic is experimentally confirmed.
On-axis diffractional behavior of two-dimensional pupils
2010
We show that, at any Fresnel number, a suitable one-dimensional Fourier transform relates the complex-amplitude distribution along the optical axis with the zero-order circular harmonic of the amplitude transmittance of a two-dimensional diffracting screen. First, our general result is applied to recognize that any rationally nonsymmetric screen generates an axial-irradiance distribution that exhibits focal shift. In this way we identify a wide set of two-dimensional screens that produce the same focal shift as that produced by the clear circular aperture. Second, we identify several apodizers for shaping the axial-amplitude distribution. We discuss some examples for achieving high-precisio…
Polyadic devil's lenses.
2009
Devil’s lenses (DLs) were recently proposed as a new kind of kinoform lens in which the phase structure is characterized by the “devil’s staircase” function. DLs are considered fractal lenses because they are constructed following the geometry of the triadic Cantor set and because they provide self-similar foci along the optical axis. Here, DLs are generalized allowing the inclusion of polyadic Cantor distributions in their design. The lacunarity of the selected polyadic fractal distribution is an additional design parameter. The results are coined polyadic DLs. Construction requirements and interrelations among the different parameters of these new fractal lenses are also presented. It is …
Continuously Variable Periodic Test Target
1987
CONTINUOUSLY VARIABLE PERIODIC TEST TARGETP. ANDRES*, J. OJEDA- CASTANEDAt, and J.C. BARREIRO*tINAOE, Apartado Postal 216, 72000 Puebla, Pue., Mexico*Departamento de Optica, Universidad de Valencia, 46100 Burjasot, Spain1. INTRODUCTIONThe modulus of the optical transfer function (MTF) of the eye or any other optical system is usuallyevaluated by imaging either several gratings each with different spatial frequency, or a single test tar-get having patterns with different frequencies (USAF resolution chart). In any of these two usual proce-dures, the measurement of the MTF is made at discrete values of the spatial frequency.Here we describe a method based on the self -imaging phenomenon for p…
Impact of anisotropy on the noncritical squeezing properties of two-transverse-mode optical parametric oscillators
2013
In a series of articles we studied the quantum properties of a degenerate optical parametric oscillator tuned to the first family of transverse modes at the subharmonic. We found that, for a cavity having rotational symmetry respect to the optical axis, a TEM$_{10}$ mode with an arbitrary orientation in the transverse plane is emitted above threshold. We proved then that quantum noise induces a random rotation of this bright TEM$_{10}$ mode in the transverse plane, while the mode orthogonal to it, the so-called dark mode, has perfect quadrature squeezing irrespective of the distance to threshold (noncritical squeezing). This result was linked to the spontaneous rotational symmetry breaking …
Analytical characterization of spectral anomalies in polychromatic apertured beams
2006
Abstract The power spectrum of polychromatic apertured spherical waves changes strongly in the vicinity of phase singularities. A spectral shift effect is observed and, in some cases, a spectral switch occurs together with a broadening of the power spectrum. Low-order moments of the power spectrum are evaluated in points of the focal volume with spectral anomalies. First-order analytical expressions are proposed for the evaluation of the relative spectral shift and the relative spectral broadening in the transverse focal plane and along the optical axis. The influence of the fractional bandwidth and the selected singularity order is considered.
Chromatic compensation in the near-field region: shape and size tunability
2005
We report a diffractive-lens triplet with which to achieve wavelength compensation in the near field diffracted by any aperture. On the one hand, the all-diffractive triplet allows us to tune, in a sequential way, the Fresnel-irradiance shape to be achromatized by changing the focal length of one diffractive lens. On the other hand, we can adjust the scale of the chromatically compensated Fresnel diffraction field by shifting the aperture along the optical axis. Within this framework, we present an extremely flexible white-light Fresnel-plane array illuminator based on the kinoform sampling filter. A variable compression ratio and continuous selection of the output pitch are the most appeal…
Achromatic Fourier transforming properties of a separated diffractive lens doublet: Theory and experiment
1998
The strong chromatic distortion associated with diffractive optical elements is fully exploited to achieve an achromatic optical Fourier transformation under broadband point-source illumination by means of an air-spaced diffractive lens doublet. An analysis of the system is carried out by use of the Fresnel diffraction theory, and the residual secondary spectrum (both axial and transversal) is evaluated. We recognize that the proposed optical architecture allows us to tune the scale factor of the achromatic Fraunhofer diffraction pattern of the input by simply moving the diffracting screen along the optical axis of the system. The performance of our proposed optical setup is verified by sev…
White-light optical implementation of the fractional fourier transform with adjustable order control.
2000
An optical implementation of the fractional Fourier transform (FRT) with broadband illumination is proposed by use of a single imaging element, namely, a blazed diffractive lens. The setup displays an achromatized version of the FRT of order P of any two-dimensional input function. This fractional order can be tuned continuously by shifting of the input along the optical axis. Our compact and flexible configuration is tested with a chirplike input signal, and the good experimental results obtained support the theory.
Dyakonov-like surface waves in the THz regime
2016
Abstract Here we examine Dyakonov-like surface waves (DSWs) in the THz regime traveling along the plane interface between a non-conducting isotropic medium and a low-loss graphene-based uniaxial metamaterial with the optic axis (OA) oriented along with the interface. New insights concerning the propagation characteristics of DSWs are given by analyzing the dispersion relation in such configuration, that is evaluated using the effective medium theory. The range of angles with respect to the OA which is determined for the in-plane wave vector can be conveniently tuned with extremely flexibility in opposition with DSWs excited in natural anisotropic media. The properties discussed here are of …