Development of passive ultrafast fiber lasers at telecom wavelengths using indium nitride as saturable absorber

This thesis focuses on the research of new technologies for fabrication of passive ultrafast mode-locked fiber lasers, operating at telecom wavelengths (C-band, 1.53-1.57 μm). For this purpose novel saturable absorbers based on indium nitride (InN) are proposed, which have been deposited using molecular beam epitaxy. This material presents unique properties such as direct band gap energy, high thermal and chemical stability, and high radiation hardness. In this thesis, the InN based structures have been completely characterized, being particularly detailed the optical characterization of both the linear and nonlinear behavior. The developed devices have demonstrated high nonlinear optical effects, with modulation depth over 30%. Moreover, they have proved to support over 100 mJ/cm2, with no sign of apparent optical damage, converting them in promising devices for high energy applications. Also, the design and fabrication of laser resonators have been carried out. For this purpose, optical fiber has been used as active medium, besides the InN-based saturable absorbers for achievement of the mode-locking. The developed lasers deliver ultrashort pulses (200-250 fs) with high peak power (over 40 kW). Furthermore, all the lasers using InN based saturable absorbers have exhibited properties such as polarization independence or self-starting operation. For all the experiments that have been performed along this work, InN can be situated as a promising material for application in the design of ultrafast lasers with emission at telecom wavelengths

Widely power-tunable polarization-independent ultrafast mode-locked fiber laser using bulk InN as saturable absorber

The growing demand of ultrafast mode-locked fiber lasers in the near infrared has boosted the research activity in this area. One of the most convenient ways to achieve passive mode locking consists of inserting a semiconductor saturable absorber in the laser cavity to modulate the losses. However, in such a configuration, the limited power range of operation is still an unsolved issue. Here we report the fabrication of an ultrafast, high-power, widely power-tunable and non-polarization-dependent mode-locked fiber laser operating at 1.55 μm, using an InN layer as saturable absorber. With post-amplification, this laser delivers 55-fs pulses with a repetition rate of 4.84 MHz and peak power in the range of 1 MW in an all-fiber arrangement

A new ultrafast and high peak power fiber laser operating at 1.5 μm using In N as Saturable Absorber

This work describes a novel ultrafast (<250 fs) fiber laser operating at 1.5 μm and based on InN as saturable absorber (SA). This SA accommodates much higher fluencies than comparable semiconductor or graphene-based SA

Development of AlInN photoconductors deposited by sputtering

In this work, we have developed photoconductor devices based on Al0.39In0.61N layers grown on sapphire by reac-tive radio-frequency magnetron sputtering. The fabricat-ed devices show a sublinear dependence of the photocur-rent as a function of the incident optical power. The above-the-band-gap responsivity reaches 7 W/A for an ir-radiance of 10 W/m2 (405 nm wavelength). The response decreases smoothly for below-the-bandgap excitation, dropping by more than an order of magnitude at 633 nm. The devices present persistent photoconductivity effects associated to carrier trapping at grain boundaries.Ministerio de Economía y CompetitividadComunidad de MadridUniversidad de Alcal

Effect of the residual doping on the performance of InN epilayers as saturable absorbers for ultrafast lasers at 1.55µm

We report on the improvement of performance of InN-based saturable absorbers in fiber lasers operating at 1.55 mum by reducing the residual doping, due to the lower Burstein-Moss effect. The improved tuning of the band-to-band transition with respect to the operation wavelength leads to an enhancement of nonlinear optical effects, resulting in 30 % of modulation depth. We introduce the development of an ultrafast mode-locked fiber laser using an improved InN-based saturable absorber that incorporates a buffer layer between the active layer and the substrate. The laser delivers output pulses with a temporal width of 220 fs, a repetition rate of 5.25 MHz, and high-pulse energy of 5.8 nJ.Ministerio de Economía, Industria y CompetitividadMinisterio de Ciencia, Innovación y UniversidadesComunidad de Madri

Diacutaneous fibrolysis intervention in patients with mild to moderate carpal tunnel syndrome may avoid severe cases in elderly: A randomized controlled trial

Producción CientíficaBackground: Carpal Tunnel Syndrome (CTS) mainly affects adults of working age. The prevalence of severe cases is higher in elderly patients (>65 years old). Clinical guidelines recommend conservative treatment as the best option in the initial stages of CTS to avoid severe cases. Diacutaneous Fibrolysis (DF) has demonstrated to improve nerve conduction studies and mechanosensitivity. The main purpose was to quantify changes in the cross-sectional area (CSA) of the median nerve, transversal carpal ligament (TCL) thickness, numbness intensity, and the subjective assessment of clinical change after DF treatment in patients with CTS. Methods: a double-blind, randomized, placebo-controlled trial was designed. A number of 44 patients (60 wrists) with CTS were randomized to the DF group or the sham group. CSA and TCL thickness variables were registered by ultrasound. Clinical variables were assessed by the visual analogue scale and GROC scale. SPSS version 24.0 for MAC was used for statistical analysis. The group by time interaction between groups was analyzed using two-way repeated measures analysis of variance. Results: The DF group reduced CSA with a mean of 0.45 mm2 (IC 95% 0.05 to 0.86) and TCL thickness with a mean reduction of 0.4 mm (IC 95% 0.6 to 2.1) compared to the sham group (p < 0.01, p < 0,03, respectively). Additionally, the DF group decreased the numbness intensity with a mean reduction of 3.47 (IC 95% 2.50 to 4.44, p < 0.01) and showed a statistically significant improvement on the GROC scale (p < 0.01). Conclusions: DF treatment may significantly reduce CSA and TCL thickness, numbness intensity, and improved clinical perspective. DF applied in patients with mild to moderate CTS may prevent the progression of the disease as they age

Sub-250 fs, 650 kW Peak Power Harmonic Mode-Locked Fiber Laser with InN-based SESAM

43rd. European Conference on Optical Communication (ECOC 2017), Gothemburg, 17-21 Sept.We demonstrate ultrafast harmonically mode-locked fiber lasing in up to 6-km-long rings at 1.56μm with InN SESAM. Fundamental mode-locking with pulse width of 239fs, pulse energy of 155nJ and peak power of 650kW is achieved with a 1-km-long cavity.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri