Fiber Laser Setup Research Articles

Multi-wavelength fiber laser via evanescent field confinement with Al2O3 nanolaminate-coated thinned fiber

We present the fabrication and analysis of an Erbium-doped optical fiber laser emitting at multiple wavelengths. This is accomplished via a filter constructed from a fiber taper coated with alumina (Al2O3). The taper is created using the flame brushing induction technique with a combination of Butane (25 %) and Oxygen (75 %). The diameter is reduced to a 20 µm waist and 2 mm burner displacement. The thin film of Al2O3 was deposited via atomic layer deposition (ALD), resulting in a 15 nm layer. The coated fiber taper was then inserted into a ring fiber laser cavity functioning as a selector filter. This fiber laser produced an output comprising six simultaneous wavelengths: 1531.14, 1531.79, 1532.45, 1541.85, 1544.45, and 1562.22 nm. Laser signal stability tests were performed for one hour at 25 °C at the six emission wavelengths, resulting in a maximum optical power fluctuation of 0.15 to 0.33 dB, a wavelength shift variation of 0.02 nm, and a signal-to-noise ratio of 31.79 dB in average. The laser lines emitted have an average spectral width of 0.06 nm. Our results show that the typical performance of the fiber laser configuration based on an optical fiber taper was improved by the addition of the Al2O3 layer and can be further improved. Our findings demonstrate that the standard operation of the fiber laser setup, which utilizes an optical fiber taper, was enhanced through the incorporation of an Al2O3 layer and has the potential for further development.

Ultrafast fiber laser at 1570 nm based on organic material as saturable absorber

In this work, we demonstrated Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) as a saturable absorber (SA) to produce mode-locking operation in different length of Erbium-doped fiber laser (EDFL). The PEDOT: PSS was embedded into polyvinyl alcohol to form a thin film that acts as an absorber into the laser setup. The three different mode-locked EDFL were successfully demonstrated with different cavity length and output coupler ratio. The pulse repetition rate/width of 3.417 MHz/710 fs, 4.831 MHz/510 fs, and 6.049 MHz/460 fs were obtained by utilizing optical coupler/ cavity length of 20:80/60.7 m, 10:90/42.7 m, and 5:95/33.7 m, respectively. All experiments generated a stable and mode-locked operation at a central wavelength of 1570.76 nm, 1570.3 nm, and 1569.95 nm with 3 dB bandwidth of 4.8 nm, 5.6 nm, and 6.5 nm, respectively. The long-time stability of the ultrafast fiber lasers was investigated for each setup via 120 min. The proposed PEDOT: PSS has proven as a promising material to induce mode-locking operation in different fiber laser setup.

Nanostructured Large Mode Area Fiber for Laser Applications

We developed a passive silica based large mode area fiber with the nanostructured core with a diameter of 30 m devoted to fiber Bragg grating inscription for application in an all-fiber laser cavity. The fiber is perfectly matched to the commercial active fiber with NA=0.06 and core/cladding diameters 30/250 m. Measured modal characteristics and bending loss of the fiber confirm single-mode operation for bending diameter of 8 cm with bending losses as low as 0.15 dB/m. Although the nanostructured fiber core is low germanium doped, we fabricated high reflectivity (98.5%) UV induced fiber Bragg grating (FBG) and verified its performance in fiber laser setup. The laser cavity formed with highly reflective FBG inscribed in the fiber and Fresnel reflection on the free end of active fiber results in lasing efficiency of 65.5%. The flexibility of the nanostructuring approach gives prospects for the development of free-form large mode area fibers for passive fiber components and matched with any type of active fibers.

On-demand generation of soliton molecules through evolutionary algorithm optimization.

Combining evolutionary algorithm optimization with ultrafast fiber laser technology, we report on the self-generation of stable two-soliton molecules with controllable temporal separation. A fiber laser setup including an adjustable virtual saturable absorber achieved through nonlinear polarization evolution and an intracavity pulse shaper is used to generate two-soliton molecules with a user-defined 3-8 ps internal delay.

Extremely robust femtosecond written fiber Bragg gratings for an ytterbium-doped fiber oscillator with 5 kW output power.

We present highly robust fiber Bragg gratings (FBGs) in passive large-mode-area fibers for kilowatt fiber laser systems. The gratings were inscribed directly through the fiber coating using near-infrared femtosecond laser pulses and then implemented in an all-fiber ytterbium-doped single-mode oscillator setup reaching up to 5 kW signal output power. The untreated cooled FBGs showed thermal coefficients as low as ${1}\;{\rm K}\;{{\rm kW}^{ - 1}}$1KkW-1, proving excellent qualification for the implementation into robust high-power fiber laser setups.

TE-like mode analysis of microsystem InGaAsP/InP semiconductor resonator generating 20 GHz repetition rate pulse trains

Abstract In microsystem technologies, the microring resonators (MRRs) can be used as a filter device. A wavelength-selective modified add-drop MRR filter is used for adding and dropping a particular wavelength in order to control the light propagation within the system. The spectrum of the mode-locked laser could be generated using a fiber laser loop consisting of active gain medium, EDF, Lumics 980 nm laser diode (LD), wavelength division multiplexer (WDM), isolator, a polarization controller (PC) and carbon nanotube (CNT). The multi-mode-locked laser could be generated at the through and drop port of the system after the mode-locked pulse from the fiber laser circulate within the MRR filter. Here, the mode-locking relies on a fiber laser setup, where the MRR filter has been modeled using the Fimmwave and PICWave softwares. We present this photonic circuits simulator based on the time-domain traveling wave (TDTW) method, provides modeling both active and passive photonic circuits. The pulse bandwidth and repetition of the train mode-locked pulses generated by the fiber laser setup are 0.65 ps and 30 MHz respectively. Using the MRR filter, the drop port output pulses show the FSR and FWHM of 172 pm (20 GHz) and 8.3 pm respectively. The finesse and the Q-factor are approximately 20.72 and 1.9 × 105 respectively.

Effect of Curcumin-Nanoemulsion Associated with Photodynamic Therapy in Cervical Carcinoma Cell Lines.

Cervical cancer is the fourth cause of cancer death in women. Curcumin has antineoplastic properties. Furthermore, curcumin may be used as a photosensitizing agent in Photodynamic Therapy. This study aimed to investigate the effects of Photodynamic Therapy in cellular viability using curcumin-nanoemulsion as a photosensitizing drug in cervical carcinoma cell lines. The empty nanoemulsion presented very low cytotoxicity in all cell lines analyzed. Additionally, the incubation with curcumin-nanoemulsion at 20 μM of curcumin showed more than 80% of cell viability for cell lines. Nanoemulsions were shown to be internalized inside cells by fluorescence microscopy and were observed in the intracellular environment for up to 36 hours after incubation with cell lines. In addition, after the Photodynamic Therapy we observed a high phototoxic effect of the curcumin-nanoemulsion with less than 5% of viable cells after irradiation. This was accompanied by an increase in caspase-3/caspase-7 activities after cell treatment with curcumin-nanoemulsion and Photodynamic Therapy, suggesting cell death by apoptosis. We conclude that the curcumin-nanoemulsion formulation behaves as a photosensitizing drug in Photodynamic Therapy and shows potential as an alternative treatment to cervical lesions using an endoscopic diode fiber laser setup for in situ activation or cavity activation using a diffuse fiber delivery system.

Bi2Te3 based passively Q-switched at 1042.76 and 1047 nm wavelength

In this paper, we propose and demonstrate the generation of dual wavelength based photonic crystal fiber passively Q-switched using few-layer TI:Bi2Te3 (bismuth telluride) saturable absorbers in a 1 micron waveband. The system employs a few-layer bismuth, induced onto a fiber ferrule using a dry oven method. A centered dual-wavelength output at 1042.76 and 1047.0 nm was produced from the Ytterbium doped fiber laser setup by incorporating 10 cm of photonic crystal fiber and finely adjusting the polarization controller. The self-started Q-switch had a pump power of 132.15 mW and a frequency ranging from 3.79 to 15.63 kHz. Therefore, TI:Bi2Te3 was suitable as a potential broadband SA in a 1 micron region.

Study of a Hi-Bi FOLM for tunable and dual-wavelength operation of a thulium-doped fiber laser.

We report a study of an all-fiber Tm-doped fiber laser with tunable single wavelength emission and dual-wavelength generation operating in different laser wavelength ranges depending on the Tm-doped fiber (TDF) length. The wavelength selection and tuning for single wavelength laser operation and the adjustment of cavity losses for dual wavelength laser operation is obtained by temperature variations of the high birefringence fiber loop in a fiber optical loop mirror. Stable dual wavelength operation is achieved at the single wavelength tuning limits when cavity losses are balanced to generate two simultaneous laser lines with equal powers. A linear cavity fiber laser setup with TDF lengths of 2, 4, 8 and 12 m is used to obtain tunable single wavelength operation in a range of ~40 nm for each TDF length. A total tuning range of ~110 nm with the four different TDF lengths is achieved. At dual-wavelength laser operation the wavelength separation was ~48 nm. The maximal power efficiency of ~34.9% with a maximum output power of 274 mW was obtained with the use of TDF length of 4 m.

The generation of passive dual wavelengths Q-switched YDFL by MoSe2 film

A simple ytterbium doped fiber laser (YDFL) setup was used to generate Q-switching pulses by using a D-shaped polished fiber as a wavelength selective filter. The gain medium used in the cavity was ytterbium doped fiber with length 70 cm. By utilizing a MoSe2 film as saturable absorber into the cavity, a stable dual wavelength was produced at 1036.69 and 1039.22 nm. The wavelength separation of the output spectrum was 2.53 nm. We found a maximum pulse energy of 0.99 nJ and shortest pulse width of 1.2 µs. We have determined consistent dual-wavelength Q-switching pulses for the 1-micron region.

Using a black phosphorus saturable absorber to generate dual wavelengths in a Q-switched ytterbium-doped fiber laser

Using a few-layer black phosphorus (BP) thin film that acts as a saturable absorber (SA) in an ytterbium-doped fiber laser setup, we experimentally demonstrated a passively dual-wavelength Q-switching laser operation. The setup also incorporated a D-shaped polished fiber as a wavelength selective filter. As the SA was used in the ring cavity, a dual-wavelength Q-switch produced consistent outputs at 1038.68 and 1042.05 nm. A maximum pulse energy of 2.09 nJ with a shortest pulse width of 1.16 µs was measured for the achieved pulses. In addition, the repetition rate increased from 52.52 to 58.73 kHz with the increment of the pump level. Throughout the measurement process, the results were obtained consistently and this demonstrates that the BP film is a very good candidate to produce Q-switching pulses for the 1 micron region.

DFB fiber laser static strain sensor based on beat frequency interrogation with a reference fiber laser locked to a FBG resonator.

We report on a high-resolution static strain sensor developed with distributed feedback (DFB) fiber laser. A reference FBG resonator is used for temperature compensation. Locking another independent fiber laser to the resonator using the Pound-Drever-Hall technique results in a strain power spectral density better than Sε(f) = (4.6 × 10-21) ε2/Hz in the frequency range from 1 Hz to 1 kHz, corresponding to a minimum dynamic strain resolution of 67.8 pε/√Hz. This frequency stabilized fiber laser is proposed to interrogate the sensing DFB fiber laser by the beat frequency principle. As a reasonable DFB fiber laser setup is realized, a narrow beat frequency line-width of 3.23 kHz and a high beat frequency stability of 0.036 MHz in 15 minutes are obtained in the laboratory test, corresponding to a minimum static strain resolution of 270 pε. This is the first time that a sub-0.5 nε level for static strain measurement using DFB fiber laser is demonstrated.

Several Mode-Locked Pulses Generation and Transmission over Soliton Based Optical Transmission Link

<p>A soliton-based optical communication system is presented to generate and transmits several mode locked laser pulses (generated by fiber laser setup) over 50 km fiber and 120 m wireless link. The passive mode-locking feature of the laser system proposed in this paper is based on nonlinear polarization rotation evolution.</p>

Extended tunability of Nd-doped fiber lasers operating at 872-936 nm.

Efficient operation of an Nd-doped fiber laser operating in a wavelength-tunable configuration using a volume Bragg grating (VBG) is reported in this Letter. A high-power operation on the 4F3/2-4I9/2 transition of Nd3+ at short wavelengths below 900 nm is demonstrated for the first time in silica fibers. A high-efficiency (47% laser conversion) output power up to 22 W and a narrow linewidth of 0.035 nm are achieved. This configuration is compared with a more conventional fiber laser setup using a bandpass filter and a highly reflective dichroic mirror.

Pulse dynamics in carbon nanotube mode-locked fiber lasers near zero cavity dispersion.

We numerically and experimentally analyze the output characteristics and pulse dynamics of carbon nanotube mode-locked fiber lasers near zero cavity dispersion (from 0.02 to ~-0.02 ps(2)). We focus on such near zero dispersion cavities to reveal the dispersion related transition between different mode-locking regimes (such as soliton-like, stretched-pulse and self-similar regimes). Using our proposed model, we develop a nanotube-mode-locked fiber laser setup generating ~97 fs pulse which operates in the stretched-pulse regime. The corresponding experimental results and pulse dynamics are in good agreement with the numerical results. Also, the experimental results from soliton-like and self-similar regimes exhibit the same trends with simulations. Our study will aid design of different mode-locking regimes based on other new saturable absorber materials to achieve ultra-short pulse duration.

A Thermal Splicing Method to Join Silica and Fluoride Fibers

Even though the melting temperatures of silica and fluoride glass are very different, a new thermal splicing method to join these fibers is presented here. The lowest attenuation achieved was about 0.2 dB. Moreover, this thermal splice was stabilized, packed and inserted in a simple fiber laser setup.

Direct airborne acoustic wave modulation of Fabry–Perot fiber laser (FPFL) over 100 kHz of operating bandwidth

The idea of applying a simple Fabry-Perot fiber laser (FPFL) set-up in a free-running condition as an acoustic sensing medium is proposed. Conventional optical microphone requires a stringently aligned diaphragm to mediate the acoustic impedance mismatch between air and silica fiber. Motivated by the difficulty of optical sensing of airborne acoustic waves, a new sensing method is proposed to sense acoustic waves without the assistance of a diaphragm as transducer. By studying the output power fluctuation of the FPFL, the operating bandwidth and sensitivity of the proposed sensing method are determined. The tunability of the resonant frequency from 5 kHz to 85 kHz allows sensing of acoustic waves in the range of 100 Hz to 100 kHz. Tuning of the resonant frequency can be performed by changing the optical pumping power from as low as 10 mW to 68.5 mW or higher.

Single-polarization ultra-large-mode-area Yb-doped photonic crystal fiber

We report on an ytterbium-doped single-transverse-mode rod-type photonic crystal fiber that combines the advantages of low nonlinearity and intrinsic polarization stability. The mode-field-area of the fundamental mode is as large as 2300 microm(2). An output power of up to 163 W with a degree of polarization better than 85% has been extracted from a simple fiber laser setup without any additional polarizing element within the cavity than the fiber itself. The beam quality has been characterized by a M(2) value of 1.2. The single-polarization window ranges from 1030 to 1080 nm, hence possesses an excellent overlap with the gain profile of ytterbium-doped silica fibers. To the best of our knowledge this fiber design has the largest mode-field-diameter ever reported for polarizing or even polarization maintaining rare-earth-doped double-clad fibers.

Efficient narrow-linewidth volume-Bragg grating-locked Nd:fiber laser

A neodymium doped microstructured large mode area fiber is frequency locked with a volume Bragg grating. This configuration is compared with a conventional fiber laser setup. A high efficiency (51% slope), stable output and a drastically narrowed linewidth (<0.07nm) are achieved.

Group interactions of dissipative solitons in a laser cavity: the case of 2+1

What can be the outcome of the interaction between a dissipative soliton pair and a soliton singlet? We report an experimental observation of ???elastic??? collisions as well as ???inelastic??? formation of triplet soliton states in a fiber laser setup. These observations are supported with the numerical simulations based on the dispersion (parameter) managed cubic-quintic Ginzburg-Landau equation model.