Browsing by Author "Kerse, Can"

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    1.7-GHz intra-burst repetition rate Yb-fiber amplifier system
    (IEEE, 2015) Kalaycıoğlu, Hamit; Elahi, Parviz; Kerse, Can; Akçaalan, Önder; İlday, F. Ömer
    Material processing efficiency of ultrafast pulses increases dramatically with repetition rate of the pulses, if the conditions are adjusted correctly to avoid excessive plasma and particulate shielding. However, given that there is a minimum pulse energy requirement, continuous operation at high repetition rates can be detrimental due to too much average power leading to heat accumulation. Burst-mode operation of lasers, wherein the amplifier periodically produces a group of pulses (a burst), which are very closely spaced in time, avoids this problem. However, ultrafast burst-mode lasers are typically limited to several 100 MHz intra-burst repetition rates. While this is sufficient for most materials, metals with high thermal conductivity require higher repetition rates.
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    Ablation-cooled material removal at high speed with femtosecond pulse bursts
    (OSA, 2015) Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Akçaalan, Önder; Yavaş, S.; Aşık, M. D.; Kesim, Deniz Koray; Yavuz, Koray; Çetin, Barbaros; İlday, Fatih Ömer
    We report exploitation of ablation cooling, a concept well-known in rocket design, to remove materials, including metals, silicon, hard and soft tissue. Exciting possibilities include ablation using sub-microjoule pulses with efficiencies of 100-mJ pulses.
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    All-fiber burst mode femtosecond laser system integrated with OCT for cataract surgery
    (IEEE, 2015) Kesim, Denizhan Koray; Kalaycıoglu, Hamit; Kerse, Can; İlday, F. Ömer
    Cataract condition is responsible for two thirds of preventable visual impairments afflicting nearly 190 million all over the world [1]. Every year, 19 million cataract surgeries are performed worldwide [2]. Femtosecond laser-assisted cataract surgery has entered clinical use in recent years as an efficient and safe alternative to the traditional method. However, this laser-assisted surgery is in its infancy period and would benefit from lower pulse energies (to minimize collateral effects), shorter operation durations, and more compact laser systems. Fiber lasers can address these requirements with their robustness, compact size and minimal-alignment requiring structure. Further, burst mode operation [3], where high repetition rate pulses are delivered in packets repeated at a relatively low rate, have been shown to produce efficient ablation with minimal collateral thermal effects [4]. Here, we demonstrate the first fiber based burst-mode femtosecond laser device for cataract surgery. The laser is coupled to an optical coherence tomography (OCT) system with computerized controls (Fig. 1(a)). A home built all fiber Yb laser amplifier is seeded by a 109-MHz fiber oscillator, followed by a double-clad preamplifier, acusto optic modulator (AOM) pulse picker and a double-clad power amplifier. An FPGA based electronic system triggered by the oscillator is used to impose the desired pulse train on the laser beam. The system is able to produce pulses in the 5-10 µJ range compressible to sub-500 fs. The imaging and tissue processing functions are executed with OCT monitoring, using its galvo scanner and a common beam path. Maximum imaging depth is 1.6 mm with 8 µm axial resolution. The galvo scanner can reach a scan speed of 1 m/s with any desired scanning pattern. In our preliminary experiments, bursts comprising of 8 pulses with 3 µJ per pulse at 50 kHz burst repetition rate were applied to agar jells (Fig. 1 (b)), which have optical response similar to that of the cornea, as well as cornea obtained from cow eyes. Smooth cuts on ex vivo cow cornea by raster scan pattern with 70% overlapping spots (Fig 1. (c)) and on agar jells with non-overlapping spots pattern (Fig 1. (d)) were obtained. Agar and ex vivo cow eye trials show that we can create incisions with different patterns below the surface, in addition to dotted patterns for corneal incision and smooth lines for capsulorhexis.
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    High-speed, thermal damage-free ablation of brain tissue with femtosecond pulse bursts
    (IEEE, 2016) Kerse, Can; Yavaş, Seydi; Kalaycıoğlu, Hamit; Asik M.D.; Akçaalan, Önder; İlday, F. Ömer
    We report a novel ultrafast burst mode fiber laser system and results on ablation of rat brain tissue at rates approaching an order of magnitude improvement over previous reports, with no discernible thermal damage. © 2015 IEEE.
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    Non-thermal material and tissue processing with 100 MHz and 500 MHz repetition rate bursts
    (IEEE, 2013) Kerse, Can; Kalaycıoğlu, Hamit; Akaalan O.; Eldeniz, Y.B.; İlday, F. Ömer; Hoogland H.; Holzwarth, R.
    There are a number of applications that would avail a pulse pattern in the form of closely grouped and uniformly spaced pulses, i.e., bursts [1]. Closely grouped pulses with pulse to pulse separation in the order of a few nanoseconds have a potential for increasing material removal rates [2] and thereby reducing the thermal effects. Besides, keeping the burst repetition period in the order of thermal relaxation time has the advantage of keeping the overall average power at lower levels in order to prevent the cumulative heating of the material. © 2013 IEEE.
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    Ultrafast micromachining of Cu and Si at ultra-high repetition rates with pulse bursts
    (IEEE, 2016) Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Yavuz, Koray; Mirza I.; Bulgakova N.M.; İlday, F. Ömer
    We report a novel ultrafast burst mode fiber laser system, which can deliver pulses at ultra-high repetition rates in order to systematically investigate micromachining efficiency on copper and silicon samples. © 2015 IEEE.