Holographic Printing Research Articles

Crosstalk image intensity reduction for color holograms by using reference beam coded with multicolored aperture array filter

The analytical form for the reconstructed field of a hologram illuminated by a reference beam coded with a multicolored aperture array filter is derived. Experiments showed that the colored aperture array filter improved the quality of the reconstructed image by reducing the intensity of crosstalk images. Some parameters of the aperture array configuration that influence image quality were investigated. This technique presented here can be applied to full-color holographic displays and dot matrix holographic printers, etc.

Three-dimensional imaging with monocular cues using holographic stereography

Two quantitative criteria are derived to evaluate monocular cues in holographic stereograms. We find that the reconstruction has correct monocular cues when the whole scene is located in a so-called "monocular cues area" with compatible monocular and binocular cues. In contrast, incorrect monocular cues appear when the scene is in the other two areas, namely, the "visible multi-imaging area" and the "lacking information area." A pupil-function integral imaging algorithm is developed to simulate monocular observation, and a holographic printing system is set up to fabricate full-parallax holographic stereograms. Both simulations and experiments agree with the criteria.

Personalized Holographic Stereogram Printer.

Personalized Holographic Stereogram Printer.

Asymmetric twin-waveguide 1.55-μm wavelength laser with a distributed Bragg reflector

We demonstrate a single frequency, 1.55 /spl mu/m wavelength laser based on an asymmetric twin-waveguide structure using a single growth step and a simple fabrication process. The external Bragg grating is formed on the passive ridge waveguide, optically coupled to the twin-guide gain section using a low loss, tapered mode transformer. The grating is produced by near-field holographic printing using a phase mask. Output powers >11 mW in a small-spot waveguide with a side-mode suppression ratio >40 dB and a slope efficiency of 0.11 W/A are obtained under pulsed operation. These performance characteristics are comparable to conventional, nonintegrated, conventional discrete DBR lasers, although the twin-waveguide design is compatible with photonic integrated circuits such as monolithic transmitters and WDM coherent receivers.

Optical configuration and color-representation range of a variable-pitch dot matrix holographic printer

The optical system configuration and design of a dot matrix holographic printer that can create image grating pixels of variable size, arbitrary pitch, and discretionary angle on a photoresist plate are presented. With the capability to vary spot size, grating orientation, and grating pitch on the fly, this newly developed holographic printer can apply a prespecified color at each specific viewing angle. Diffractive images with various visual effects and the wide color range that are possible by use of this system are examined in detail.

Dynamic holographic imaging of the beating human heart

Background--Currently, the reporting and archiving of echocardiographic data suffer from the difficulty of representing heart motion on printable 2-dimensional (2D) media. Methods and Results--We studied the capability of holography to integrate motion into 2D echocardiographic prints. Images of normal human hearts and of a variety of mitral valve function abnormalities (mitral valve prolapse, systolic anterior motion of the mitral leaflets, and obstruction of the mitral valve by a myxoma) were acquired digitally on standard echocardiographic machines. Images were processed into a data format suitable for holographic printing. Angularly multiplexed holograms were then printed on a prototype holographic "laser" printer, with integration of time in vertical parallax, so that heart motion became visible when the hologram was tilted up and down. The resulting holograms displayed the anatomy with the same resolution as the original acquisition and allowed detailed study of valve motion with side-by-side comparison of normal and abnormal findings. Comparison of standard echocardiographic measurements in original echo frames and corresponding hologram views showed an excellent correlation of both methods (P<0.0001, r2=0.979, mean bias=2.76 mm). In this feasibility study, both 2D and 3D holographic images were produced. The equipment needed to view these holograms consists of only a simple point-light source. Conclusions--Holographic representation of myocardial and valve motion from echocardiographic data is feasible and allows the printing on a 2D medium of the complete heart cycle. Combined with the recent development of online holographic printing, this novel technique has the potential to improve reporting, visualization, and archiving of echocardiographic imaging.

Resist profile enhancement in near field holographic printing using bottom anti-reflection coatings

Holographic lithography and near-field holography (NFH) used to print gratings in the manufacture of DFB lasers are limited in the quality of the resist profiles due to the effects of vertical standing waves occurring within the photoresist layer. We report on various attempts to produce improved grating profiles in photoresist which can thereby directly serve as dry etch masks for transferring gratings into semiconductors. Trials include both thin dielectric layers as well as bottom antireflection coatings (BARC's) to mitigate interference effects. We show that among these, a bilayer BARC/photoresist method is both practical and can greatly improve resist profiles.

Wavelength uniformity in λ/4 shifted DFBlaser array WDMtransmitters

Six-element quarter-wave-shifted DFB arrays have been fabricated using holographic printing with e-beam generated quartz phase masks. A standard deviation of s = 0.18 nm from a uniform WDM channel spacing has been achieved, a dramatic improvement over the values associated with wafer-wide DFB wavelength distributions.

Advances in near field holographic grating mask technology

We report progress on several practical issues of near field holographic (NFH) printing for optoelectronic applications. In particular, we report on the following: adaptation of the mask making process to large area holographically generated grating masks; evaluation of a commercially available UV contact aligner modified to allow routine NFH printing; use of mask copies to avoid excessive wear on original masks; options for reducing the writing time for e-beam generated grating masks; and the application of e-beam generated grating masks to a DFB six-laser array with 200-GHz frequency channel separation.

Multiwavelength distributed Bragg reflector laser array fabricated using near field holographic printing with an electron-beam generated phase grating mask

We describe near optimum near field holography grating masks patterned by e-beam lithography and a distributed Bragg reflector (DBR) multiwavelength laser array fabricated using near field printing with this mask. Grating pitches in the array ranged from 242.861 to 243.750 nm in 0.127 nm steps. Data on the pitch precision and pitch adjustment is presented. Use of a conventional UV source rather than laser illumination both greatly simplified the printing process and eliminated coherent artifacts from the printed gratings. Chemically etched InP test gratings are shown to be extremely ‘‘clean’’ in appearance and low in edge roughness. DBR laser arrays designed with 100 GHz frequency separation were processed using the mask described. The measured frequency separation was 99 GHz which could be further adjusted with a tuning section of the four-section laser design. Characterization of a similar grating mask containing 16 wavelengths with similar pitch increments is also described.

Characterization of near-field holography grating masks for optoelectronics fabricated by electron beam lithography

Direct write e-beam lithography and reactive ion etching was used to fabricate square-wave gratings in quartz substrates which serve as pure phase masks in the near-field holographic printing of gratings. This method of fabricating these masks extends the flexibility of the printing technique by allowing both abrupt phase shifts as well as multiple grating pitches to be simultaneously printed from a single contact mask. Grating masks with periods in the 235–250 nm range have been produced and measured to be within 0.15 nm of the design period. Transmitted and diffracted beam powers have also been measured for various duty cycles and etch depths and are shown to be important parameters for ‘‘balancing’’ these interfering beams. Simple scalar diffraction modeling is used to qualitatively examine the dependence of diffraction on grating parameters, but the need for a more comprehensive modeling is illustrated. Prototype masks have been used to produce grating patterns on InP substrates using two different ultraviolet illumination sources: an argon ion laser and a conventional mercury lamp.