Multibound soliton formation in an erbium-doped ring laser with a highly nonlinear resonator

We have studied the generation of low-noise ultrashort multibound solitons in the telecommunication spectral window in an erbium-doped all-fiber ring laser with a highly-nonlinear resonator mode-locked by a nonlinear polarization evolution effect. The multibound soliton generation is obtained with more than 20 bound dechirped pulses with a duration of 240 fs at a repetition rate of 11.3 MHz (with a signal-To-noise ratio of 73.3 dB), the relative intensity noise is <-140 dBc/Hz, and the Allan deviation of the repetition frequency does not exceed $\sim 1.3\cdot 10^{\mathbf {-8}}$ with a time averaging window of 100 s

Multibound solitons generation with a controllable number of bound states in a passive mode-locked all-fiber erbium-doped ring laser

We have studied generation of stable and low-noise de-chirped ultrashort solitons in bound states and we have experimentally demonstrated the formation multi-bound solitons with the controllable number of bound states 7 < N < 17 by pump power variation. A numerical simulation of the influence of various types of fluctuations on the generation mode was also carried out

Femtosecond Er-Doped All-Fiber Laser with High-Density Well-Aligned Carbon-Nanotube-Based Thin-Film Saturable Absorber

International audienceWe have studied the ultrafast saturation behavior of a high-density well-aligned single-walled carbon nanotubes saturable absorber (HDWA-SWCNT SA), obtained by a high-pressure and high-temperature treatment of commercially available single-wall carbon nanotubes (SWCNTs) and related it to femtosecond erbium-doped fiber laser performance. We have observed the polarization dependence of a nonlinear optical saturation, along with a low saturation energy level of <1 fJ, limited to the detector threshold used, and the ultrafast response time of <250 fs, while the modulation depth was approximately 12%. We have obtained the generation of ultrashort stretched pulses with a low mode-locking launching threshold of ~100 mW and an average output power of 12.5 mW in an erbium-doped ring laser with the hybrid mode-locking of a VDVA-SWNT SA in combination with the effects of nonlinear polarization evolution. Dechirped pulses with a duration of 180 fs were generated, with a repetition rate of about 42.22 MHz. The average output power standard deviation was about 0.06% RMS during 3 h of measurement

Non-Invasive Acoustic Monitoring of Gas Turbine Units by Fiber Optic Sensors

In this article, we study the possibility of gas turbine unit (GTU) monitoring using interferometric fiber optic sensors. We used the Mach&ndash;Zehnder interferometer (MZI) scheme, which can be easily implemented and simply installed on the turbine, and also allows us to solve the problem of phase unwrapping conveniently. In this research, the following main steps were carried out: an experimental scheme based on the MZI was assembled, and its sensitive arm was fixed on the GTU under study; data on various operation modes of the GTU was collected; the data were subjected to frequency FFT analysis, based on which the main rotational speeds of the turbine were identified. With FFT analysis, we also demonstrated multiples harmonics, which appear in the case of GTU after operating time, caused by the number of blades. The possibility of GTU monitoring and analysis using a non-invasive compact fiber-optic sensor is demonstrated: spectral analysis is used to detect the rotor speed, as well as the presence or absence of high-order multiple frequencies indicating blade and bearing defects, which are determined by the number of GTU&rsquo;s blades and rolling bearing used as turbines rotor supports

Growth Features of Bi2Te3Sb1.5 Films on Polyimide Substrates Obtained by Pulsed Laser Deposition

Thermoelectric materials in the form of thin films are used to create a wide variety of sensors and devices. The efficiency of these devices depends on the quality and efficiency of the thermoelectric materials obtained in the form of thin films. Earlier, we demonstrated that it is possible to obtain high-performance Bi2Te3Sb1.5 films less than 1 &mu;m thick on polyimide substrates by using the PLD method, and determined optimal growth conditions. In the current work, the relationship between growth conditions and droplet fraction on the surface, microstructure, grain size, film thickness and chemical composition was studied. A power factor of 5.25 &mu;W/cm&times;K2 was achieved with the reduction of droplet fraction on the film surface to 0.57%. The dependencies of the film thickness were studied, and the effect of the thickness on the efficiency of the material is shown. The general trend in the growth dynamics for Bi2Te3Sb1.5 films we obtained is the reduction of crystalline size with Pressure-Temperature (PT) criterion. The results of our work also show the possibility of a significant reduction of droplet phase with simultaneous management of crystalline features and thermoelectric efficiency of Bi2Te3Sb1.5 films grown on polyimide substrates by varying growth conditions

Properties of Scalable Chirped-Pulse Optical Comb in Erbium-Doped Ultrafast All-Fiber Ring Laser

We report on a scalable chirped-pulse Er-doped all-fiber laser, passively mode-locked by single-wall carbon nitride nanotubes. The average output power is ~15 mW, which corresponds to a peak power of ~77 W, and pulse energy of ~1.9 nJ and was achieved using a single amplification stage. We observed chirped-pulse generation with a duration of ~24.6 ps at a relatively low repetition rate of ~7.9 MHz, with a signal-to-noise ratio of ~69 dB. To characterize the short-term stability of the obtained regime, we have measured the relative intensity noise of the laser, which is &lt;−107 dBc/Hz in the range of 3 Hz–1000 kHz. It should be noted that the standard deviation of root mean square of average power does not exceed a magnitude of 0.9% for 3 h of measurement

Femtosecond Er-Doped All-Fiber Laser with High-Density Well-Aligned Carbon-Nanotube-Based Thin-Film Saturable Absorber

We have studied the ultrafast saturation behavior of a high-density well-aligned single-walled carbon nanotubes saturable absorber (HDWA-SWCNT SA), obtained by a high-pressure and high-temperature treatment of commercially available single-wall carbon nanotubes (SWCNTs) and related it to femtosecond erbium-doped fiber laser performance. We have observed the polarization dependence of a nonlinear optical saturation, along with a low saturation energy level of &lt;1 fJ, limited to the detector threshold used, and the ultrafast response time of &lt;250 fs, while the modulation depth was approximately 12%. We have obtained the generation of ultrashort stretched pulses with a low mode-locking launching threshold of ~100 mW and an average output power of 12.5 mW in an erbium-doped ring laser with the hybrid mode-locking of a VDVA-SWNT SA in combination with the effects of nonlinear polarization evolution. Dechirped pulses with a duration of 180 fs were generated, with a repetition rate of about 42.22 MHz. The average output power standard deviation was about 0.06% RMS during 3 h of measurement

Study of Intra-Chamber Processes in Solid Rocket Motors by Fiber Optic Sensors

In this study, an experimental study of the burning rate of solid fuel in a model solid propellant rocket motor (SRM) E-5-0 was conducted using a non-invasive control method with fiber-optic sensors (FOSs). Three sensors based on the Mach&ndash;Zehnder interferometer (MZI), fixed on the SRM E-5-0, recorded the vibration signal during the entire cycle of solid fuel burning. The results showed that, when using MZI sensors, the non-invasive control of solid fuel burnout is made possible both by recording the time of arrival of the combustion front to the sensor and by analyzing the peaks on the spectrogram of the recorded FOS signal. The main mode of acoustic vibrations of the chamber of the model SRM is longitudinal, and it changes with time, depending on the chamber length. Longitudinal modes of the combustion chamber were detected by MZI only after the combustion front passed its fixing point, and the microphone was unable to register them at all. The results showed that the combustion rate was practically constant after the first second, which was confirmed by the graph of the pressure versus time at the nozzle exit