ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING Peer Reviewed and Refereed Journal IMPACT FACTOR: 2.104 (ISSN NO. 2456-1037) Vol.03, Issue 09, Conference (IC-RASEM) Special Issue 01, September 2018 Available Online: www.ajeee.co.in/index.php/AJEEE
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STUDY OF PARAMETERS FOR OPTICAL FIBER TIP FABRICATION FOR BESSEL BEAM GENERATION
Pallavi, Anoop Gorshi
Haryana Engineering College Jagadhri, Haryana, India e-mail address: [email protected]
Abstract: In this letter, we have studied the different parameters for optical fiber tip fabrication for Bessel beam generation. The tip is prepared by chemical etching process in hydro fluoric (HF) acid solution in a tube under the influence of capillary action. Typical tip features are short taper length, large cone angle and small probe tip dimension which enhances light throughput and light efficiency. During the fabrication of optical fiber tip typical parameters are study that are etching time, effect of temperature, diameter of tube for HF acid solution , length of fiber dip in HF acid solution tube. By optimization of these parameters we can control the shape of fiber tip. These parameters are varies for different photosensitive single mode fiber. Parameters are different for every fiber because of their optical, geometrical and mechanical specifications. The optical fiber tip is used in near field optics and far field optics for research. The optical fiber tip may be ideal low cost probe for SNOM, SERS detection and other sensors, scanning and imaging applications.
CIS code; (060.2270) Fiber characterization, (120.4610) Optical fabrication, (060.2310) Fiber optics
1. INTRODUCTION
Optical fiber tip is an optical component which finds many and strong applications in interdisciplinary research. The tip of different dimensions, nanometer to micrometer, is prepared by modifying optical fiber tip for controlling the far field and near-field optics. Several approaches and techniques are used for tip shaping which is used to changes light spot and divergence, improving optical efficiency, and redirecting light without the addition of discrete optical components within the system’s optical path [1]. The most common structure of fiber tips are taper fiber tip, lenses, diffusers, sidefire and angled ends.Positive axicon lens is for generation for Bessel beam (BB)[2]. The Bessel beam, introduced by Durmin in 1987 and has many applications in optical manipulation [3]. It would be interesting to fabricate and study tip on optical fiber facet for generating Bessel beam.
2. EXPERIMENT
Fabrication of Optical Fiber Tip: In the experiment we have fabricated optical fiber tip by chemical etching.in hydrophobic tube. 48% hydrofluoric (HF) acid is used as etching agent [4, 5]. The etching rate for cladding and core in acid solution creates capillary ring along core- cladding boundary. The capillary ring is filled with HF acid due to surface tension and capillary action. The techniques create near perfect symmetric tip at the
apex of fiber. During the etching process the height of acid level in capillary ring decreases while width of ring increases.
Toluene being lighter is used to cover free surface of the acid solution preventing evaporation of the toxic acid. The optical fiber tip is dipped inside HF with specified height in the tube.The doping of core of optical fiber with photosensitive material increases the etching rate of core in HF acid. Combined with surface tension, capillary action, etching rate difference and hydrophobic tube, the Optical fiber tip is automatically developed at the distal end of fiber under certain conditions [6].
Fig.1 (a) Hydrophobic tube having HF acid for optical fiber tip fabrication (b)
Optical fiber tip fabrication setup Fig. 1 (a) is the picture of Hydrophobic tube which contained HF acid and
ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING Peer Reviewed and Refereed Journal IMPACT FACTOR: 2.104 (ISSN NO. 2456-1037) Vol.03, Issue 09, Conference (IC-RASEM) Special Issue 01, September 2018 Available Online: www.ajeee.co.in/index.php/AJEEE
2 toluene. Fig. 1 (b) is a fabrication setup of optical fiber tip. A cleaved optical fiber is inserted into tube and placed it distal end below the meniscus.
However, the tip structure and optics strongly depends upon the type of optical fibers. We have Fabricated optical fiber tips in three different type of fiber like FUD, CMS-HP and GF3
3. RESULTS
The resulted optical fiber tip in core is imaged by optical microscope. For observation of Bessel beam the one end of fiber is coupled to a laser source & beam emitted from tip is showed on a screen.
Fig 2 shows Bessel beam of three different fiber from the modified tip. During the experiment we have studied the different parameters like effect of temperature, Etching timing, Diameter of tube, length of fiber dip in HF acid. These parameters affect the Beam quality and stability and the structure of the tip. We optimized etching time and temperature for three different types of fiber. Comparative results shown in table-I
To study the quality of Beam, images are taken by digital camera. From fig we study the Bessel beam has bright central spot with maximum intensity and side rings has lower intensity as compare to center spot. This shows maximum intensity has high depth of focus of beam.
Fig.2Microscopic image of (a) CMS - HP(b) GF3 (c) FUD-3837. Each row corresponds to Bessel beam, optical microscope image for the respective
optical fiber
4. CONCLUSION
We have compared fabrication of optical fiber tip from different type of fibers and the respective Bessel beams by optimization of parameters. From the all results it is observed that though optical fiber tip is formed on all type of fibers, the FUD -3837 & CMSHP has symmetric results of fiber tip but FUD-3837 & GF3 fiber generates Bessel beam.
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