Three-mode Laser Research Articles

Model of a tunable hybrid Tamm mode-liquid crystal device.

A concept of an easily tunable device based on hybrid Tamm modes is proposed. The device can be controlled using a high-sensitivity chiral liquid crystal serving as a mirror. The coupling of the chiral optical Tamm state with the Tamm plasmons is predicted. The Tamm plasmons are excited at different frequencies for the orthogonal linear polarizations, while the chiral Tamm state is excited at only one frequency. The properties of the proposed model are analytically and numerically calculated. The possibility of creating a two- and three-mode laser with tunable characteristics on the basis of the proposed model is discussed.

Intracavitary laser obliteration of Baker cyst under ultrasonic navigation

Relevance. Baker's cyst is the formation in the popliteal region, resulting from the accumulation of synovial fluid in the semimembranous bursa due to anastomosis between the joint cavity and the synovial bursa of the popliteal region. Trauma and/or some inflammatory diseases of the joints are the main causes of these cysts. Despite the success of endoscopic methods of treatment of this category of patients, the frequency of postoperative complications is 3-10%.
 The aim is to conduct a comparative analysis of the Baker's cysts treatment results using intracavitary laser obliteration and traditional cyst excision.
 Materials and methods. The treatment results of 39 patients with Baker cysts, who entered the clinic for the period from 2012 to 2017, are analyzed. Patients were divided into 2 representative groups. Ultrasound-guided intracavitary laser obliteration of Baker's cyst was performed in 24 (62%) patients of the main group. Traditional radical excision of all cyst elements with application of the primary suture was performed for 15 (38%) patients of the control group. A russian single-wave programmable three-mode laser scalpel LSP - "IRE-Polyus" was used in the work.
 Results. The patients of the main group had almost no pain syndrome, the duration of hospital treatment and rehabilitation were 4 times shorter than in the group of traditional operations (p≤0,05). Satisfaction with the laser treatment results of the patients from this group was 83.3%, while in the traditional treatment group - only 66.6%.
 Conclusion. The minimum number of the disease recurrences after ultrasonic-controlled intracavitary laser obliteration of Baker's cysts, the simplicity and low-traumatism of manipulation, the low level of complications, coupled with the high patient satisfaction with the treatment results, set apart this technology from traditional one, which allows recommending this method for wide application.

The distribution mechanism of noise fluxes between three oscillating modes of a free-running class-A laser

In the present work, we have extended the noise features of a class-A laser from the single-mode state with one oscillating freedom to the three-mode state with three oscillating freedoms. The laser noise is modeled by the cavity Langevin force in the absence of other two atomic population inversion and dipole moment Langevin forces. The Maxwell-Bloch equations of motion are thus solved in the presence of three cavity Langevin forces associated with the simultaneous oscillations of cavity central mode and its left and right adjacent modes. Therefore, the phase and amplitude fluctuations of electric field components that are oscillating at the three consecutive longitudinal modes have analytically been calculated in frequency domain. The results of our calculations indicate that the cavity Langevin force of each of three oscillating modes makes a direct contribution in producing the noise fluxes of other two oscillating modes. We have also determined the exact share of each oscillating mode in the total output intensity noise spectra of a three-mode laser. It is finally demonstrated that the input noise flux of laser pumping is distributed between the output noise fluxes of spontaneous and stimulated emission radiations of three oscillating modes according to the flux conservation law.

Calculation and analysis of the number of return photons from sodium laser beacon excited by the long pulse laser with circular polarization

The number of return photons from sodium laser beacon (SLB) greatly suffers down-pumping, recoil, and geomagnetic field when the long pulse laser with circular polarization interacts with sodium atoms in the mesosphere. Considering recoil and down-pumping effects on the number of return photons from SLB, the spontaneous radiation rates are obtained by numerical computations and fittings. Furthermore, combining with the geomagnetic field effects, a new expression is achieved for calculating the number of return photons. By using this expression and considering the stochastic distribution of laser intensity in the mesosphere under different turbulence models for atmosphere, the number of return photons excited by the narrow-band single mode laser and that by the narrow-band three-mode laser are respectively calculated. The results show that the narrow-band three-mode laser with a specific spectrum structure has a higher spontaneous radiation rate and more return photons than a narrow-band single mode laser. Of note, the effect of the atmospheric turbulence on the number of return photons is remarkable. Calculation results indicate that the number of return photons under the HV5/7 model for atmospheric turbulence is much higher than that under the Greenwood and ModHV models.

Rate-equation model for multi-mode semiconductor lasers with spatial hole burning

We present a set of rate equations for the modal amplitudes and carrier-inversion moments that describe the deterministic multi-mode dynamics of a semiconductor laser due to spatial hole burning. Mutual interactions among the lasing modes, induced by high- frequency modulations of the carrier distribution, are included by carrier-inversion moments for which rate equations are given as well. We derive the Bogatov effect of asymmetric gain suppression in semiconductor lasers and illustrate the potential of the model for a two and three-mode laser by numerical and analytical methods.

Theory of gain and mode locking in free-running class-B lasers with simultaneous oscillation of three longitudinal modes

The operation of a three-mode laser with a homogeneous broad bandwidth is modeled as three different harmonic oscillators coupled to each other by the usual Maxwell–Bloch equations. The main aim is to extend and compare the laser variables when it moves from a single to a three-mode state. A multi-component model for the cavity electric field and the atomic population inversion is introduced to describe the simultaneous oscillation of the laser central and adjacent modes. The phase relations and the frequency shifts of these components in mode-locking conditions are determined. We also investigate the effect of the laser pumping rate and the mode frequency separation on the amplification of modes. Finally, the amplification gains of all three modes are calculated and their agreement with the energy conservation law is demonstrated.

A Low-Nonlinearity Laser Heterodyne Interferometer with Quadrupled Resolution in the Displacement Measurement

Quantitative analysis has been applied extensively for modeling and compensation of periodic nonlinearities since the invention of heterodyne laser interferometers. In this article, we mathematically analyze and modele the nonlinearity resulting from non-orthogonality and ellipticity of the polarized laser beams for a modified high-resolution nano-displacement measuring system based on a three-mode laser interferometer. Also, we present a simple method to compensate for the periodic nonlinearity in the modified system based on a two-mode type nonlinearity reduction method. The results reveal that the factor of nonlinearity reduction can reach a value of 99.9% for some special cases of deviations resulting from non-ideal polarized light. In addition to the nonlinearity compensation, we show that the resolution of the displacement measurement in the modified system is doubled and quadrupled with respect to the conventional three- and two-mode laser heterodyne interferometers, respectively.

Dynamical characterization of chaotic itinerancy in a three-mode laser subjected to frequency-shifted optical feedback

We investigated chaotic dynamics in a microchip three-mode solid-state laser subjected to frequency-shifted optical feedback. When the frequency shift was tuned to harmonic frequencies of the relaxation oscillation, a bifurcation from a periodic sustained relaxation oscillation ("soft-mode") state to a chaotic spiking ("hard-mode") state via a chaotic itinerancy was observed as the feedback intensity was increased. Dynamic characterizations of modal interplay and self-induced switching between the soft- and hard-mode chaotic states over times (i.e., chaotic itinerancy) were carried out by the information circulation analysis and joint time-frequency analysis of long-term experimental time series. Drastic changes in information transfer rates among oscillating modes and occasional frequency locking among periodicities of two chaotic states associated with switchings were identified in chaotic itinerancy. Essential dynamical behaviors were reproduced by numerical simulation.

Noise-driven switching and chaotic itinerancy among dynamic states in a three-mode intracavity second-harmonic generation laser operating on a Lambda transition.

We studied the antiphase self-pulsation in a globally coupled three-mode laser operating in different optical spectrum configurations. We observed locking of modal pulsation frequencies, quasiperiodicity, clustering behaviors, and chaos, resulting from the nonlinear interaction among modes. The robustness of [p:q:r] three-frequency locking states and quasiperiodic oscillations against residual noise has been examined by using joint time-frequency analysis of long-term experimental time series. Two sharply antithetical types of switching behaviors among different dynamic states were observed during temporal evolutions; noise-driven switching and self-induced switching, which manifests itself in chaotic itinerancy. The modal interplay behind observed behaviors was studied by using the statistical dynamic quantity of the information circulation. Well-organized information flows among modes, which correspond to the number of degeneracies of modal pulsation frequencies, were found to be established in accordance with the inherent antiphase dynamics. Observed locking behaviors, quasiperiodic motions, and chaotic itinerancy were reproduced by numerical simulation of the model equations.

Collective chaos synchronization of pairs of modes in a chaotic three-mode laser.

We study chaos synchronization experimentally in a modulated globally coupled three-mode laser with different modal gains subjected to self-mixing Doppler-shifted feedback, which can apply the loss modulation to individual modes at Doppler-shift frequencies. Depending on the pump power, different forms of collective chaos synchronizations were found to appear when the laser was modulated at the highest relaxation oscillation frequency, reflecting the change in cross-saturation coefficient among modes. In the present experiment, each pair of modes exhibited phase, lag, or generalized synchronization collectively according to the inherent antiphase dynamics, where these types of synchronization have already been demonstrated in two coupled chaotic oscillators in different physical systems. Information flows among oscillating modes which are established in different forms of collective chaos synchronizations were characterized by information-circulation analysis of the experimental time series. (c) 2002 American Institute of Physics.

Laser-controlled state excitation and quantum computation

Based on the dependence of the molecular excitation probabilities on the laser phases and amplitudes in the model of a three-mode laser interacting with a three-level molecule, we propose a scheme to implement quantum XOR logic gate and to construct quantum error prevention code.

Antiphase dynamics and self-pulsing due to a low-frequency spatial population grating in a multimode laser

We study analytically equations that extend the Tang-Statz-deMars rate equations for a multimode Fabry-Perot laser by including the low-spatial-frequency population grating and the inhomogeneous pumping rate along the cavity axis [Quant. Semiclassic Opt. 5, L17 (1997)]. First, we prove the theorem that is the foundation of the antiphase dynamics: The total intensity transients are characterized by only one frequency, the single-mode relaxation oscillation. Second, we study the three-mode laser operation. In this context, we derive analytic expressions for the steady-state intensities, their linear stability, and the bifurcation points. We prove that strictly multimode solutions display a Hopf bifurcation leading to passive Q-switched solutions. Numerically, we have found that these time-periodic regimes may bifurcate to quasiperiodic and chaotic states and that there are many domains of bistability.

Accurate Stabilization of a 3 mW Single-Mode Output He-Ne Laser by Intermittent Frequency Offset Locking to an Iodine Stabilized He-Ne Laser

A high-power, unmodulated frequency standard laser light with low running cost is a powerful tool for industrial measurement involving laser calibration and interferometry in length and shape. To obtain such a laser light, we developed an intermittent frequency offset locked laser (IFOL laser). This laser system, composed of an iodine stabilized He-Ne laser (I2SL) and a high-powered symmetric three-mode He-Ne laser (HP-3ML, optical output=5 mW), provides two stabilization operational modes: (1) independent mode (I-mode) and (2) slave mode (S-mode). Utilizing the frequency pulling effect, HP-3ML is stabilized at the condition of symmetric three-mode oscillation, and a 3 mW single-mode light with frequency instability of 10-12 is obtained (I-mode). When the optical frequency deviates from the allowed limit during I-mode, HP-3ML is temporarily offset-locked to I2SL (S-mode) with frequency resettability of 10-10 and frequency instability of 10-12. After completion of the drift reset in S-mode, HP-3ML is stabilized in I-mode again, and then I2SL is turned off. In a typical case of allowed drift in ±1 MHz, repetitive operation of I-mode for 10 days and S-mode for 5 min was satisfactory. Such an intermittent operation reduces the working time of I2SL dramatically, resulting in low running cost that enables long-term use in industrial measurement.

Intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser

There is a need for an intense, unmodulated single-frequency stabilized laser light that guarantees absolute optical frequency in a rapid laser calibration or an ultra-high resolution interferometer. To obtain such a light, we developed a new laser system that uses an intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser. The proposed laser system provides two operational modes: (1) independent and (2) slave mode. In the independent mode, frequency of the three-mode laser is stabilized via control of frequency difference between two intermode beats. The resultant output is a single longitudinal mode light of maximum intensity that locates at the top of the gain curve. Frequency instability of 8X10-12 (at a sampling time of 100 s) which is better than conventional stabilized lasers is attained in the independent mode. Slow optical frequency drift during the independent mode is periodically corrected by the offset lock to the iodine stabilized laser (slave mode), resulting in accurate reset of the frequency drift. After reset of the frequency deviation, the three-mode laser is again operated in the independent mode. Due to such intermittent offset lock, duty factor of the iodine stabilized laser was reduced to a few % of continuous operation.

Dependence of the linewidth of a semiconductor laser on the mode distribution

A theory and measurements that show the dependence of the frequency noise spectrum and, therefore, of the semiconductor laser linewidth on the mode distribution are presented. The theory is based on rate equations where the linewidth is strongly influenced by the gain saturation coefficients (nonlinear gain). Analytical results are restricted to two modes. Measurements show that the linewidth change of the main mode depends on the wavelength side of the side mode (related to the wavelength mode of the main mode) and the effect decreases with increasing mode separation. Furthermore, the theoretical and measured frequency noise spectra of a three-mode laser are depicted, showing a characteristic resonance peak for certain mode distributions. This property of the frequency noise spectrum is also described by the theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Frequency resonance in a three-mode laser with a nonlinearity absorbing cell

A three-mode method for the separation of frequency resonances in a laser with a nonlinear absorbing medium is proposed. The results are reported of a study of frequency resonances in an He?Ne/I2 laser emitting the wavelength of 0.63?. It was found that the three-mode method ensures considerable enhancement of the frequency resonance gain compared with the two-mode method, which is desirable in spectroscopic applications of lasers and in the stabilization of the laser emission frequency.

The quantum theory of a three-mode laser

The density operator theory and method are used to extend the fully quantum-mechanical theory of the two-level single-mode laser advanced by Sargent, Scully and Lamb (1974) to the homogeneously broadened four-level atomic system so that the master equation of the three-mode laser operation for this system is obtained. The steady-state operation characteristics of the laser in different cases are discussed and compared. Especially, pictorial comparison and discussion of the quantum-statistical properties of the laser are carried out by means of numerical computation. Meanwhile some experimental results obtained by Otsuka (1978) are qualitatively explained.

Measurement of small displacements with a three-mode laser

Measurement of small displacements with a three-mode laser

Total intensity of a three-mode laser under mode-locked conditions

A numerical analysis of the three-mode Lamb model of an He–Ne laser operating under mode-locked conditions is used to show that there is a spectrally narrow singularity in the dependence of the total intensity on the mode frequency. The position of this singularity coincides with the center of the line due to the active transition. The calculated parameters of the effect at λ = 0.63 μ indicate that it can be used in frequency stabilization.

Theory of self-locking phenomena in the pressure broadened three-mode He-Ne laser

Taking account of pressure broadening the coefficients in Lamb's third-order amplitude and phase determining equations for three modes are evaluated in the Doppler limit, and comparison is made with other theories. After expanding the coefficients to first order in the detuning e from the linecenter an expression is presented for the frequency range where mode locking will occur.