Showing papers on "Lens (optics) published in 2022"

Experimental Studies Into the Beam Parameter Product of GaAs High-Power Diode Lasers

Abstract: Experimental studies into the beam parameter product ( BPP ) of 940–980 nm GaAs-based high-power diode lasers are presented. Such lasers exhibit broadening far field and narrowing near field with increasing bias, with BPP increasing tenfold over the diffraction limit. First, spectrally-resolved beam profile measurements of lasers with monolithically-integrated gratings are presented, showing that a reproducible series of spatially-extended optical modes makes up the optical field. Then, changes to the device construction are presented, enabling effects limiting BPP to be inferred and addressed. Process- and package-induced effects can be minimized by design, while the effects of carrier, gain and temperature profiles dominate. Self-heating within the laser stripe raises the refractive index, forming a thermal lens, and the variation in curvature of this lens with bias and device construction directly affects BPP . Temperature non-uniformity along the resonator is also shown to strongly degrade BPP . Moreover, current spreading and the resulting lateral carrier accumulation (LCA) amplify high-order, high- BPP modes, thus degrading BPP for any given thermal lens. This LCA-induced degradation is shown to be suppressed by regrown lateral current-blocking structures. Finally, a flatter thermal lens and lower BPP can be achieved using thermal engineering, via changes to the epitaxial design or device layout.

Design of a real-time fiber-optic infrared imaging system with wide-angle and large depth of field

Abstract: A key limitation in the observation of instruments used in operations and heart sutures during a procedure is the scattering and absorption during optical imaging in the presence of blood. Therefore, we propose a novel real-time fiber-optic infrared imaging system simultaneously capturing a flexible wide field of view (FOV) and large depth of field infrared image in real time. The assessment criteria for imaging quality of the objective and coupling lens have been optimized and evaluated. Furthermore, the feasibility of manufacturing and assembly has been demonstrated with tolerance sensitivity and the Monte Carlo analysis. The simulated results show that the optical system can achieve a large working distance of 8 to 25 mm, a wide FOV of 120°, and the relative illuminance is over 0.98 in the overall FOV. To achieve high imaging quality in the proposed system, the modulation transfer function is over 0.661 at 16.7 lp/mm for a 320×256 short wavelength infrared camera sensor with a pixel size of 30 µm.

Polychromatic annular folded lenses using freeform gradient-index optics

Abstract: The annular folded lens (AFL) is a design form offering large aperture, high-resolution imaging in a very axially compact package. The folded optic can be made monolithic for easier fabrication and alignment, yet the introduction of refractive surfaces with a dispersive optical material gives way to chromatic aberrations. AFL designs using homogeneous media are generally limited to the monochromatic regime, with polychromatic performance greatly reduced. By introducing freeform gradient-index (F-GRIN) media, monolithic AFL designs can achieve higher monochromatic performance as well as provide color correction for diffraction-limited polychromatic imaging. Monochromatic and polychromatic design methodologies are surveyed where the F-GRIN is constrained to remain feasible for fabrication.

Nanoparticle trapping by counter-surface plasmon polariton lens

Abstract: A counter-surface plasmon polariton lens (CSPPL) is proposed to perform stable nanoparticle trapping by providing up to 120kbT optical potential depth. The optical potential depth is related to the incident angle and phase difference of the light incident on two gratings of CSPPL. The depth of optical potential can be manipulated with negligible displacement by the incident angle less than 20°. Both the depth and the center position of the optical potential well can be manipulated by the incident phase difference. The study of stable and manipulatable optical potential on the CSPPL promotes the integration of optical tweezers.

Ofloxacin-Loaded Niosome-Laden Contact Lens: Improved Properties of Biomaterial for Ocular Drug Delivery.

Abstract: Currently, bacterial conjunctivitis is managed by multiple antibiotic eye-drop solution, which is highly inefficient due to low ocular bioavailability and frequent dosing. Therapeutic soft contact lenses can be used to sustain the release of ocular drugs. However, the conventional soaking method (economic and widely used) showed low drug uptake and high burst release, and the optophysical properties of the contact lens were altered for clinical application. In this paper, novel ofloxacin-loaded niosomes were developed to increase the drug loading capacity of contact lenses while also sustaining ocular drug delivery. Ofloxacin-loaded niosomes were prepared by the thin film hydration technique with three levels of cholesterol. The niosome-laden contact lenses (OFL-Nio-L) led to improved optophysical properties (swelling, transmittance, oxygen permeability) and lysozyme adherence compared to the conventional soaked contact lens (CV-OFL-L). The in vitro drug release data of CV-OFL-L showed high burst release, while OFL-Nio-L lenses showed sustained release up to 48-96 h. In a rabbit tear fluid model, the OFL-Nio-100-L lens showed a high drug concentration at all-time points compared to the CV-OFL-L and eye-drop solution. The efficacy study in the rabbit model showed improved healing effect with OFL-Nio-100-L lens compared to frequent eye-drop therapy. In conclusion, the paper demonstrated the successful application of niosomes to deliver ofloxacin using contact lens without affecting the critical lens properties to substitute eye-drop therapy.

Investigation on parallel auxiliary adjusting machine of spatial filter lens for a high-power laser facility

Abstract: As a key part in high-power laser facility, the spatial filter is used to determine the optical axis of the entire laser system, which consists of two conjugate lenses at both ends and filter hole in the middle. The lenses usually require precise adjustment, and the adjustment mechanism is integrated to both ends of the filter currently. To this end, a novel parallel adjusting machine for the filter lenses was proposed as an auxiliary tool in the spatial filter process. The machine was designed to realize the five-dimensional adjustment functions of the filter lenses with X-Y-Z axial translation, pitch, and yaw motion. The first-order ghost point of the filter lens was used as the feedback reference for the parallel machine to adjust Z-position of the lens. A more comprehensive optimization-oriented framework was established to improve the sensitivity of the lens to the posture error and to optimize the positioning speed based on the steepest descent method (SDM). The experimental results verified the superiority of the proposed adjustment machine and feedback reference point.

Size-dependent interband optical properties of lens-shaped InAs/InP quantum wire

Abstract: Using the combination of coordinate transformation and the finite difference method, we have studied theoretically, the optical absorption coefficient and the refractive index changes of the InAs/InP quantum wire, with a lens cross-section. For this purpose, we have used the analytical expressions for optical properties obtained by the compact-density matrix formalism. The evaluation has been performed in varying the dimension of the quantum wire and the incident optical intensity I. The obtained results show that the oscillator strength (transition life) increase (decrease) by increasing the height H. Also, the total absorption coefficient achieves a maximum value which corresponds to the energy difference of the two different electronic states and the resonant peaks shift toward the lower energies by increasing the height H.

Freeform gradient index progressive addition lens raytrace performance evaluation

Abstract: Raytrace evaluation capable of evaluating progressive addition lens (PAL) designs with freeform surface and gradient index (GRIN) contributions is presented. The method is validated on an analytically generated PAL start design and on optimized surface designs. Surface raytrace evaluations are compared with the surface-geometric evaluation commonly presented for freeform surface PAL designs. The evaluation is also tested on analytically generated freeform GRIN PAL designs with spherical and plano surfaces. The raytrace method agrees with the analytic performance and surface-geometric performance near the center of the lens and deviates at the edge of the lens, due to ray obliquity with the surfaces and aggregate contributions of surfaces and/or GRIN. These deviations are expected, as the raytrace model accounts for more physical contributions to optical performance, including pupil diameter and eye position. This raytrace method enables the evaluation of lens performance contributions other than from polished surfaces on homogeneous materials, enabling further exploration of GRIN in PAL designs.

Confocal fluorescence microscopy with high-NA diffractive lens arrays

Abstract: Traditionally, there is a trade-off between the numerical aperture and field of view for a microscope objective. Diffractive lens arrays (DLAs) with overlapping apertures are used to overcome such a problem. A spot array with an NA up to 0.83 and a pitch of 75 µm is produced by the proposed DLA at a wavelength of 488 nm. By measurement of the fluorescence beads, the DLA-based confocal setup shows the capability of high-resolution measurement over an area of 3mm×3mm with a 2.5×0.07NA objective. Further, the proposed fluorescence microscope is insensitive to optical aberrations, which has been demonstrated by imaging with a simple doublet lens.

Bioinspired lenses from cats’ eyes

Abstract: It is well known that cats have fascinating eyes with various colors, such as green, blue, and brown. In addition, they possess strong night vision ability, which can distinguish things clearly even in a poor light environment. These drive us to reveal the secrets behind them. In fact, cats’ eyes can be considered as special lenses (which we would like to mimic by using a Luneburg lens). We make an analysis of the role of photonic crystals behind the lens and demonstrate that the integration of photonic crystals into Luneburg lens can be regarded as a retroreflector and greatly improve the light focusing intensity of the lens in a broad band of frequencies. This wonderful bioinspired phenomenon is expected to design more interesting and serviceable devices by combining photonic crystals with transformation optics.

Some displays of lens structural performance

Abstract: Some useful displays that provide information about the performance of lens systems are presented and discussed in this paper. They are useful for comparing lenses, identifying problematic lens elements, and lens desensitizing and optimizing. An imaging simulation of a square wave is also presented to complement the modulation transfer function plots.

Analysis of Phase Error in Rotman Lens Design with Different Beam Angles

Abstract: Rotman lens as a multiple beam forming network is widely used in recent radar applications due to its high performance. Reduction in phase error for multi-focal two-dimensional Rotman lens design is critically demanded to obtain the optimal performance of the lens. This paper presents the analysis of path length error for tri-focal Rotman lens design for beam angles; \({30}^{\circ}\), \({35}^{\circ}\) and \({40}^{\circ}.\) The analysis of lens is mainly based on conventional relationship between parameter ‘g’ and beam angle ‘α’ and the values of ‘g’ obtained by multiple iterations through simulation. It offers better reduction in phase error corresponding to different beam angles.

Theoretical modeling and calculation of stress fields in precision optical lens subjected to multi-point adhesive bonding assembly

Abstract: In optical precision assembly, most optical components are fixed by multi-point adhesive bonding. However, the stress fields generated in lenses by radial stress in the adhesive significantly influence the imaging quality of precision optical lenses. To date, the adhesive bonding process is conducted empirically, meaning that the stress in lenses cannot be actively or quantitatively controlled. Therefore, to improve the current passive process, a theoretical mechanical model of an optical lens was established, and a novel stress potential function was proposed to derive the analytical solution of stress components in lenses under an arbitrary number of multi-point radial stresses. The results revealed a quantitative relationship between the radial stress in the adhesive and the stress field in the optical lens. Furthermore, a new experimental device was developed, and a systematic experimental method was proposed to apply multi-point quantitative radial loads on an optical lens and measure its real-time stress distribution, which further verifies the accuracy and validity of the proposed theoretical model. This study provides a theoretical approach for the quantitative control of lens stress and optimization of adhesive bonding configuration in optical precision assembly process, which is a basis to enhance the imaging accuracy of precision optical instruments.