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1

Modelling and analysis of fibre microlenses with ray-tracing and finite-difference methods

Śliwak Adam, Jeleń Mateusz, Patela Sergiusz

Opto-Electronics Review

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2022

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Vol. 30, No. 1

art. no. e140147

EN

Fibre optic microlenses are small optical elements formed on the end-faces of optical fibres. Their dimensions range from a few tens to hundreds of micrometres. In the article, four optical fibre microlenses are modelled and analysed. Microlenses are used for light beam manipulation and quantitative metrics are needed to evaluate the results, for example, the size of focusing spot or intensity distribution. All four lenses tested are made of rods of the same refractive index; they were welded to a single-mode fibre. Two modelling methods were used to analyse the lenses: ray-tracing and finite-difference time-domain. The ray-tracing algorithm moves rays from one plane to another and refracts them on the surfaces. Finite-difference time-domain consists of calculating Maxwell’s equations by replacing spatial and temporal derivatives by quotients of finite differences. In this paper, the results of the microlenses analyses obtained from ray-tracing and finite-difference timedomain methods were compared. Both mets of analysis showed the presence of undesirable side lobes related to lens design, namely rods too long for lens fabrication. The test results were compared with the measurements made with the knife-edge method. The use of a single tool to determine parameters of an optical fibre lens does not allow for precise determination of its properties. It is necessary to use different tools and programs. This allows a complete analysis of the beam parameters, letting us find the causes of technical issues that limit the performance of the lenses.

2

Realization of optical fibers terminated with ball lenses

Guzowski B., Lisik Z., Tosik G.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2016

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Vol. 64, nr 2

279--282

EN

In this article the process of realization of ball-lensed optical fibers is described. The implementation of four different types of ball-lensed optical fibers developed in Optical Fibers Techniques Laboratory at Lodz University of Technology is presented. Focal lengths of the presented microlenses, which were obtained in simulations and measurements, are also shown in this paper.

3

Hot embossing method for development of soft glass microoptic components with broadband infrared transmission

Kasztelaniec R., Buczyński R., Cimek J., Kujawa I., Stępień R., Kozłowska A., Maląg A., Waddie A. J., Taghizadeh M. R.

Elektronika : konstrukcje, technologie, zastosowania

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2014

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Vol. 55, nr 11

108-110

EN

We describe the application of the hot embossing process to fabricate micro-optical elements using soft glasses with enhanced tramsmission in mid infrared. The fabricated elements are both refractive lenses and diffractive elements) that can be used in the visible to mid-infrared range 0.5…5 μm.

PL

W artykule przedstawiono zastosowanie metody odciskania na gorąco do wytwarzania elementów mikrooptycznych ze szkieł tlenkowych wieloskładnikowych o wysokiej transmitancji w zakresie średniej podczerwieni. Metoda została użyta do wytworzenia elementów refrakcyjnych oraz dyfrakcyjnych przeznaczonych do zastosowań w zakresie szerokopasmowym od 0,5 do 5 μm.

4

Modelling of vertical-cavity surface-emitting laser beam collimation using a nanostructured gradient index microlens

Nowosielski J M, Waddie A. J., Taghizadeh M. R., Buczynski R.

Optica Applicata

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2013

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Vol. 43, nr 4

761--772

EN

In this paper we show that the recently developed nanostructured gradient index (nGRIN) rod microlens can be utilised for the collimation of the beam generated by a vertical-cavity surface-emitting laser (VCSEL). The modelling of the nanostructured lens structure is performed using the finite difference time domain (FDTD) method with realistic nGRIN parameters and a Gaussian model of the light source. The large refractive index gradient of the nanostructured microlens allows the final microlens thickness to be only 70 μm with a diameter of 10 μm. Successful collimation of a single-mode VCSEL beam with a waist half-width of 1.53 μm is presented with a reduction in divergence half-angle from 10.1° to 3.3°. We show that the linear polarisation of the incident beam is preserved as well as presenting the tolerance of this type of lens to variations in overall thickness.

5

Increasing semiconductor laser-optical fiber coupling efficiency by introducing microlens

Ozyazici M.S.

Optica Applicata

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2004

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Vol. 34, nr 2

185-202

EN

The efficiency of coupling between semiconductor lasers and single-mode optical fibers can be greatly increased by a microlens of an appropriate focal length being fabricated at the end of the fiber. The reason for this is that the lens can effectively improve the mode matching of the laser and fiber fields. Theoretical work has been carried out to predict this improvement of coupling efficiency as a function of the focal length and spot size associated with the laser and fiber. A simple method was then used to fabricate the microlenses whose focal lengths required a radius of curvature ranging from about 10 mm to 15 mm for maximum coupling. The method comprised in tapering of the fiber to the required radius using a grinder and then with an electric arc and heating the end which next forms into a hemisphere due to surface tension forces. Another way is to dip the tapered end into molten optical glass picking up a droplet of glass.