Nonlinear Mirror Research Articles

All-Polarization Maintaining Noise-Like Pulse From Mode-Locked Thulium-Doped Fiber Laser Based on Nonlinear Loop Mirror

In this paper, we present a figure-eight all-polarization maintaining thulium-doped mode-locked fiber laser based on a nonlinear optical loop mirror operating at noise-like pulse regimes. The total cavity length is 34.5 m, and the calculated net group delay dispersion is estimated to be ∼−2.616 ps <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . At the maximum pump power, stable noise-like pulse centered at 1943 nm with a spectral full width at half maximum of 32 nm, a pulse energy of 13.51 nJ, and a coherence spike width of 236 fs is generated at a repetition rate of 5.96 MHz with the signal-to-noise ratio ∼64 dB. The polarization extinction ratio is > 15 dB at any mode-locking operation. The slope efficiency and the output power fluctuation of the laser are 5.16% and 0.039%, respectively. The laser does not require polarization state controllers, and it holds very high stability, which is insensitive to temperature changes or mechanical vibrations. Through further amplification, it will be a good laser source for real-time interrogation of fiber Bragg gratings and supercontinuum generation.

Влияние структуры волнового фронта лазерного излучения на синхронные автоколебания в волоконных лазерах с микрооптомеханическими резонаторами

It is shown, that increasing the stability of synchronous self-oscillations in fiber lasers with nonlinear mirrors, based on micro-optomechanical resonators (micro-oscillators), can be achieved due to the transformation of the wavefront of laser radiation, interacting with micro-oscillators. These transformations are based on the unique properties of mode interference in composite singlemode-multimode-singlemode fiber structures.

Influence of the structure of the wavefront of laser radiation on synchronous self-oscillations in fiber lasers with micro-optomechanical resonators

It is shown, that increasing the stability of synchronous self-oscillations in fiber lasers with nonlinear mirrors, based on micro-optomechanical resonators (micro-oscillators), can be achieved due to the transformation of the wavefront of laser radiation, interacting with micro-oscillators. These transformations are based on the unique properties of mode interference in composite singlemode-multimode-singlemode fiber structures. Keywords: synchronous self-oscillations, fiber lasers, microcantilever, resonance.

Passively Mode-locked Erbium-doped Fiber Laser Based on Nonlinear Fiber Loop Mirror

Passively Mode-locked Erbium-doped Fiber Laser Based on Nonlinear Fiber Loop Mirror

The Mirror Transform

This paper explains how to describe any finite-energy signal through a unique representation consisting of an ordered set of positions and a sparse set of signals. This is obtained by designing an iterative decomposition through a series of mirror operations around those positions. The purpose is to find at any step of the decomposition the location that provides for the maximum decoupling between the even and odd components of the signal with respect to it. By limiting such even and odd components on three separate information bearing support, the algorithm can be iterated at infinity determining a sequence of positions. The per location information determines the optimal energy decoupling strategy at each stage providing remarkable sparsity in the representation. The resulting transformation leads to a 1-to-1 mapping. The approach is easily extended to finite-energy sequences, and in particular for sequences of finite length <inline-formula><tex-math notation="LaTeX">$N$</tex-math></inline-formula>, at most <inline-formula><tex-math notation="LaTeX">$N$</tex-math></inline-formula> iterations of the decomposition are required. Thanks to the sparsity of the resulting representation, experimental simulations demonstrate superior approximation capabilities of this proposed non-linear Mirror Transform with potential application in many domains such as approximation and coding. Its implementation has been made publicly available.

Femtosecond all-polarization-maintaining Nd fiber laser at 920 nm mode locked by a biased NALM.

We demonstrate a femtosecond all-polarization-maintaining Nd fiber laser working at 920 nm mode locked by a biased non-linear loop mirror. The broadest spectral width of the pulse is 25.2 nm and the output power is 8 mW with 320 mW pump power. The measured pulse width is 109 fs with extra-cavity compression. The laser configuration of all-polarization-maintaining fiber can directly enhance the environmental stability of generated pulses. The seed pulses of the oscillator were amplified over 400 mW, which served as the light source for a two-photon microscope. To the best of our knowledge, this is the first demonstration of a 920 nm femtosecond Nd polarization-maintaining fiber laser based on a non-linear loop mirror.

Nonlinear mirror image method for nonlinear Schrödinger equation: Absorption/emission of one soliton by a boundary

AbstractWe perform the analysis of the focusing nonlinear Schrödinger equation on the half‐line with time‐dependent boundary conditions along the lines of the nonlinear method of images with the help of Bäcklund transformations . The difficulty arising from having such time‐dependent boundary conditions at is overcome by changing the viewpoint of the method and fixing the Bäcklund transformation at infinity as well as relating its value at to a time‐dependent reflection matrix. The interplay between the various aspects of integrable boundary conditions is reviewed in detail to brush a picture of the area. We find two possible classes of solutions. One is very similar to the case of Robin boundary conditions whereby solitons are reflected at the boundary, as a result of an effective interaction with their images on the other half‐line . The new regime of solutions supports the existence of one soliton that is not reflected at the boundary but can be either absorbed or emitted by it. We demonstrate that this is a unique feature of time‐dependent integrable boundary conditions.

Operation of Fabry-Perot laser with nonlinear PT-symmetric mirror

Operation of Fabry-Perot laser with nonlinear PT-symmetric mirror

Delay-differential-equation model for mode-locked lasers based on nonlinear optical and amplifying loop mirrors

Delay differential equation model of a nonlinear optical--nonlinear amplifying loop mirror mode-locked laser is developed that takes into account the finite relaxation rate of the gain medium and asymmetric beam splitting at the entrance of the nonlinear mirror loop. Asymptotic linear stability analysis of the continuous wave solutions performed in the limit of large delay indicates that in a class-B laser flip instability is preceded by the modulational instability and therefore cannot give rise to stable square wave patterns. Numerically it is shown that the model can demonstrate large windows of regular fundamental and harmonic mode-locked regimes with single and multiple pulses per cavity round trip time separated by domains of irregular pulsing.

Tunable unidirectional nonlinear emission from transition-metal-dichalcogenide metasurfaces

Nonlinear light sources are central to a myriad of applications, driving a quest for their miniaturisation down to the nanoscale. In this quest, nonlinear metasurfaces hold a great promise, as they enhance nonlinear effects through their resonant photonic environment and high refractive index, such as in high-index dielectric metasurfaces. However, despite the sub-diffractive operation of dielectric metasurfaces at the fundamental wave, this condition is not fulfilled for the nonlinearly generated harmonic waves, thereby all nonlinear metasurfaces to date emit multiple diffractive beams. Here, we demonstrate the enhanced single-beam second- and third-harmonic generation in a metasurface of crystalline transition-metal-dichalcogenide material, offering the highest refractive index. We show that the interplay between the resonances of the metasurface allows for tuning of the unidirectional second-harmonic radiation in forward or backward direction, not possible in any bulk nonlinear crystal. Our results open new opportunities for metasurface-based nonlinear light-sources, including nonlinear mirrors and entangled-photon generation.

A nonlinear current mirror method for improving the slew rate of subthreshold current recycling OTAs

ABSTRACT A proposed ultra-high slew rate current recycling folded cascode OTA working in the subthreshold region is presented. By employing adaptive biasing and the proposed positive-feedback nonlinear current mirror techniques, it not only forces the charge or discharge path to enter the strong inversion region during slewing, but also provides an ultra-high output current, leading to a significant boost in the slew rate. The simulation results of the two OTAs designed in SMIC 0.18 m CMOS process demonstrate that the slew rate of our proposed OTA is enhanced 387 times than that of the conventional counterpart with the same power.

Nonlinear Absorbing-Loop Mirror Mode-Locked all-Polarization-Maintaining Yb-Doped Fiber Laser

In this paper, a nonlinear absorbing-loop mirror (NAbLM) is constructed in a polarization-maintaining (PM) version and applied in the all-normal dispersion (ANDi) regime, for the first time to our best knowledge. To investigate the properties of NAbLM in contrast with typical nonlinear optical loop mirror (NOLM), an asymmetric optical coupler is used in the NAbLM. In experiment, both the NAbLM and NOLM can be used to mode-lock a Yb-doped fiber (YDF) laser and enable a type of noise-like pulse (NLP) generation. Noticeably, however, it is further found that, in comparison to NOLM, NAbLM evidently enables both temporal and radio frequency (RF) noise suppressions, as well as elimination of RF variations. Further calculations show that the saturable property of the incorporated absorber plays a vital role in differing the NAbLM from typical NOLM. Our results demonstrate some new features of NAbLM, especially in respect to temporal pulse shaping, indicating that NAbLM can be a useful type of fiber loop mirror in nonlinear fiber optics.

Numerical study of a hybrid mode-locked erbium-doped fluoride fiber laser at 2.8 μm

We numerically investigate a hybrid mode-locked erbium-doped fluoride fiber laser in the mid-infrared region. Based on the coaction of nonlinear polarization rotation (NPR) and semiconductor saturable absorber mirror (SESAM), uniform mode-locked soliton pulse with 155 fs pulse duration, 14.78 kW peak power, and 2.29 nJ pulse energy can be achieved. For comparison, the single SESAM mode-locking and NPR mode-locking of the erbium-doped fluoride fiber laser are simulated, respectively. The effect of all kinds of parameters including gain fiber length, saturable energy of the gain fiber, linear cavity phase delay bias, and small-signal gain on the hybrid mode-locking laser are also investigated.

The Cost of Energy-Efficiency in Digital Hardware: The Trade-Off between Energy Dissipation, Energy–Delay Product and Reliability in Electronic, Magnetic and Optical Binary Switches

Binary switches, which are the primitive units of all digital computing and information processing hardware, are usually benchmarked on the basis of their ‘energy–delay product’, which is the product of the energy dissipated in completing the switching action and the time it takes to complete that action. The lower the energy–delay product, the better the switch (supposedly). This approach ignores the fact that lower energy dissipation and faster switching usually come at the cost of poorer reliability (i.e., a higher switching error rate) and hence the energy–delay product alone cannot be a good metric for benchmarking switches. Here, we show the trade-off between energy dissipation, energy–delay product and error–probability for an electronic switch (a metal oxide semiconductor field effect transistor), a magnetic switch (a magnetic tunnel junction switched with spin transfer torque) and an optical switch (bistable non-linear mirror). As expected, reducing energy dissipation and/or energy–delay product generally results in increased switching error probability and reduced reliability.

An in-band diode-end-pumped high-power and high-efficiency ultrashort pulse Nd:YVO4 bulk laser mode-locked by a frequency doubling LBO crystal

Nonlinear mirror (NLM) mode locking has also been verified to be an efficient technology for high-power ultrashort pulse laser generation. In this paper, we report on high-power and high-efficiency NLM mode-locked Nd:YVO4 laser with a 880-nm diode laser for in-band pumping, which has very rarely been investigated in the past. The achieved maximum average output power reached 6.76 W at an absorbed power of 13.82 W corresponding to a slope efficiency of 54.5%. Thanks to the used type I LBO crystal with small group velocity mismatch, the achieved pulse duration was as short as 6.5 ps. The results represent one of the best performances that ever achieved for NLM mode-locked Nd:YVO4 laser. NLM mode locking could be very promising for high-power ultrashort pulse generation in visible and middle infrared wavelengths, at which SESAMs are still not mature and the average output powers of ultrafast laser oscillators are also still limited to great extent.

A DTMOS-based power efficient recycling folded cascode operational transconductance amplifier

The focus of the present study is on a recycling folded cascode (RFC) operational transconductance amplifier (OTA) in which the transconductance, as well as the slew rate of OTA, are enhanced. RFC OTA, proposed in this study, is employed using a Dynamic Threshold Voltage MOSFET (DTMOS) based differential pair with class AB operation. To achieve class AB operation, an adaptive biasing technique comprising a flip voltage follower is used which boosts the dynamic current and gain-bandwidth product of OTA. Conventional current mirrors are replaced with source degenerated non-linear current mirrors to achieve a better slew rate. The conventional and proposed RFC structures are designed and simulated in a standard 180 nm CMOS process at 1 V supply voltage. The proposed RFC OTA demonstrates a significant enhancement in the performance parameter as 11 dB improvement in the gain as well as 290% more GBW and achieves a slew rate that is nine times better compared to the conventional RFC.

Dispersion managed thulium-doped fiber laser mode-locked by the nonlinear loop mirror

Intracavity dispersion management in a passively mode-locked thulium-doped all-fiber laser, based on a nonlinear optical loop mirror (NOLM) saturable absorber is reported. Fundamental soliton and stretched pulse soliton generation are demonstrated, when the oscillator operates with anomalous net dispersion. Gaussian pulses with a duration of 253 fs and 26.4 nm spectral bandwidth centered at wavelength of 1967 nm were generated with a fundamental pulse repetition frequency of ~15.8 MHz. In soliton mode-locking regime the oscillator delivering optical solitons with a 3 dB spectral width of 7.96 nm and duration of 675 fs. To the best of our knowledge, this is the shortest fundamental soliton generated from thulium-doped fiber laser with all anomalous dispersion based on a nonlinear fiber loop mirror saturable absorber reported till date.

Dispersion management of a nonlinear amplifying loop mirror-based erbium-doped fiber laser.

We report an investigation of dispersion management of an all-polarization-maintaining Er-fiber oscillator mode-locked via a nonlinear amplification loop mirror in a figure-nine cavity configuration with two output ports. The performance of the laser was investigated within the net cavity dispersion ranging from -0.034 ps2 to +0.006 ps2. We show that the spectral and temporal phase of the pulses at both figure-nine outputs have clearly different characteristics. One of the laser outputs provides pulses with significantly better quality; nonetheless, the rejection output also offers ultrashort pulses with broad spectra. Pulses as short as 79 fs with an energy of 83 pJ were generated directly from the laser in the near-zero dispersion regime.

Theoretical analysis of periodically poled LiNbO3 nonlinear mirror and its application in a passively mode-locked Nd:YSAG laser

In this paper, we report a passively mode-locked Nd:Y3Sc2Al3O12 (Nd:YSAG) laser using a periodically poled LiNbO3 (PPLN) superlattice. Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was theoretically analyzed. The modulation depth of nonlinear reflectivity of the nonlinear mirror is approximately 8.8%. Optical performances of the mode-locked laser including output power, radio frequency spectrum, and optical spectrum were experimentally investigated. An average output power of 710 mW with a slope efficiency of 14.6% was obtained at the pump power of 6.5 W. The repetition rate is 101.7 MHz, and the signal-to-noise ratio of the mode-locked pulse is 45 dB. The mode-locked pulse width was approximately 9 ps.

All Polarization Maintaining Fiber-Based Optical Comb System with Nonlinear Loop Mirror Mode-Locking

All Polarization Maintaining Fiber-Based Optical Comb System with Nonlinear Loop Mirror Mode-Locking