Single-frequency Output Power Research Articles

Widely tunable single-frequency Er-doped ZBLAN fiber laser with emission from 3.37 to 3.72 µm.

We demonstrate a widely tunable single-frequency Er-doped ZBLAN fiber laser operating on a 4F9/2→4I9/2 transition band. An uncoated germanium (Ge) plate serves as a narrow-bandwidth etalon and is inserted in the cavity to achieve a single longitudinal mode selection. Wavelength tuning from 3373.8 nm to 3718.5 nm was demonstrated by using a blazed diffraction grating at 3.5 µm. At the emission peak of 3465.6 nm, the laser yields over 100 mW single-frequency output power, with a 3 dB linewidth <6.9 MHz, and a slope efficiency (with respect to the incident 1990 nm pump power) of 20.3%. Such a tunable mid-infrared single-frequency fiber laser may serve as a versatile laser source in spectroscopy and sensing applications.

Single-frequency fiber laser of 315 mW at 1940 nm based on a Tm : YAG/Ho : YAG-co-derived silica fiber.

A 1940 nm single-frequency distributed Bragg reflector (DBR) fiber laser was demonstrated based on a Tm : YAG/Ho : YAG-co-derived silica fiber (THCDSF). The THCDSF, which had a core dopant concentration of 8.02 wt.% Tm2O3 and 1.18 wt.% Ho2O3, was prepared via the melt-in-tube (MIT) method using a Tm : YAG and a Ho : YAG as the precursor core and a silica tube as the cladding. Employing 1.8 cm of the THCDSF, we achieved a maximum single-frequency output power of 315 mW at 1940 nm when pumped by a 1610 nm fiber laser. The slope efficiency of the laser was 29.68% for the absorbed pump power. The laser linewidth was less than 23.65 kHz, and the relative intensity noise (RIN) stabilized at -145 dB/Hz after exceeding 4.8 MHz. To the best of our knowledge, this is the first demonstration of a single-frequency DBR laser with a Tm3+/Ho3+ fiber as the gain medium.

Dual-HR-FBG based single-frequency fiber laser at 1030 nm

We demonstrate a single-frequency fiber laser operating at 1030 nm with a distributed Bragg reflector cavity consisting of two high-reflectivity fiber Bragg gratings (HR-FBGs). By proper thermal adjustment, the gain bandwidth of the fiber laser is significantly compressed through the spectral overlap near the edges of the reflection band of two HR-FBGs, and the single-longitudinal-mode lasing is achieved. The effective cavity length of the fiber laser with the proposed cavity configuration is calculated, and its variation with the temperature difference between two HR-FBGs is also verified through the observation of the relaxation oscillation frequency shift. The measured laser linewidth is about 4.45 kHz at a temperature difference of 48.2 °C. The single-frequency output power of 14.4 mW is achieved at a pump power of 540 mW.

Watt-level 1.7-μm single-frequency thulium-doped fiber oscillator

Here we demonstrated an efficient high-power single-frequency thulium-doped fiber ring laser operating at 1720 nm. Three cascaded sub-rings were inserted into the main cavity to significantly enlarge the effective free spectral range. By incorporating a fiber Bragg grating, the single longitudinal mode operation was achieved. The maximum single-frequency output power reached up to 1.11 W under 3.75-W launched pump power, while the slope efficiency with respect to the absorbed pump power was 46.4%. The laser linewidth at maximum single-frequency power was measured of 1.9 kHz. Potential power scaling of the single-frequency output power with different quantity and lengths of the sub-rings was also theoretically investigated.

A tunable single-frequency green laser based on a wedged Nd:YVO4 crystal and a KTP crystal

A 532 nm single-frequency laser generated from a V-type oscillator configuration with a wedged Nd:YVO4 crystal and a KTP crystal is reported. An a-cut, 2.at% Nd:YVO4 crystal with a wedge angle of 10° and a KTP nonlinear crystal composes a novel birefringent filter. By adjusting the incident angle of the fundamental mode in the KTP, the laser can change from single-mode operation to two-mode oscillation. The maximum single-frequency output power of lasers with a 5 mm long KTP and a 7 mm long KTP are 284 and 148 mW, respectively, at pump powers of 2 and 1.1 W. The corresponding optical-to-optical conversion efficiencies are 14.2% and 13.5%. For the laser configuration with a 5 mm long KTP, the single-frequency operation at a pump power of 2 W is maintained within the temperature range of 18 °C to 24 °C, and the measured wavelength drift rate with the temperature is approximately 0.071 nm °C−1.

30 W single-frequency continuous-wave master oscillator power amplifier laser at 1342 nm.

We present a power-scalable high-power single-frequency continuous-wave 1342 nm master oscillator power amplifier (MOPA) system that consists of a polarized single-frequency 1342 nm LD seed laser, a Raman fiber preamplifier, and a three-stage ${\rm Nd}:{{\rm YVO}_4}$Nd:YVO4 power amplifier. The single-frequency output power of 30 W at 1342 nm is achieved with the beam quality factors ${{\rm M}^{2\:}} = {1}.{26}$M2=1.26, and the power stability for 1 h is better than ${\pm }\;{0}.{5}\% $±0.5%.

Narrow-linewidth hybrid waveguide/fiber laser at 1535 nm

A hybrid waveguide/fiber laser in single-frequency operation is demonstrated for the first time to the best of our knowledge. A resonant ring, which is used as a filter in the laser cavity to select a single longitudinal mode based on the multiple-beam interference effect, is fabricated in a SiO2-based waveguide. The resonant ring presents strong mode selection ability, by significantly increasing the loss difference between the main oscillating mode and the side modes. During the experiment, a hybrid waveguide/fiber laser is constructed with a 10 mm diameter resonant ring. The single-frequency output power of the laser is 3.5 mW at 1535 nm. The linewidth is measured to be less than 800 Hz by the delayed self-heterodyne method.

Single longitudinal mode operation in diode-end-pumped wedge Nd:YVO4 laser

Single longitudinal mode laser in a wedge Nd:YVO4 crystal with short absorption depth is reported. The influence of the wedge Nd:YVO4 crystal on single longitudinal mode operation is analyzed. Two types of Nd:YVO4 crystal with a wedge angle of 7° and 10° are utilized in a compact plane–concave resonator, respectively. By optimizing the cavity length, 518 mW and 343 mW of single-frequency output power at 1064 nm are obtained by pumping of 808 nm laser diode with an slope efficiency of 38.7% and 32.4% for 10° and 7° Nd:YVO4 crystal, respectively. For 2 at. % Nd:YVO4 laser, the experimental and theoretical multimode threshold with a wedge crystal are higher than the theoretical multimode threshold with traditional cube crystal. It has been demonstrated successfully larger wedge angle Nd:YVO4 can enhance the performance of the single mode laser.

Yb,Er:glass Microlaser at 1.5 µm for optical fiber sensing: development, characterization and noise reduction

A fiber-pumped single-frequency microchip erbium laser was developed and characterized with the aim of using it in coherent Optical Time Domain Reflectometry (OTDR) measurements and sensing. The laser is pumped by a fiber-coupled 976 nm laser diode and provides 8 mW TEM00 single frequency output power at 1.54 µm wavelength, suitable for efficient coupling to optical fibers. The amplitude and phase noise of this 200 THz oscillator were experimentally investigated and a Relative Intensity Noise (RIN) control loop was developed providing 27 dB RIN peak reduction at the relaxation oscillation frequency of 800 kHz

Impact of Tag Responsiveness on Gen2 RFID Throughput

It is well known in the research community that the throughput of dynamic frame slotted ALOHA (DFSA) in a radio frequency identification (RFID) system can be maximized when DFSA frame size is set to the number of tags. However, related works often neglect the fact that tag responsiveness is of a stochastic nature, depending on the tag hardware performance in the wireless channel. Therefore, as number of tag responses may not be equal to the number of tags located in the interrogation area, corrections to the standard simulation models should be applied. In this letter, we provide the corrections that are based on tag read probability (TRP) metrics. At first, numerically, TRP was retrieved by the usage of fully configurable open-source software defined radio RFID reader in an indoor nonfading radio channel at the single frequency and constant output power, while considering reliable communication parameters in the environment of single and a pair of commercial Gen2 RFID tags. Then, TRP is statistically modeled, and the implications to the throughput are shown.

Generation of high-power single-frequency 397.5 nm laser with long lifetime and perfect beam quality in an external enhancement-cavity with MgO-doped PPSLT.

Continuous-wave single-frequency high power 397.5 nm laser with long lifetime and perfect beam quality is one of the essential resource to generate the squeezed and entanglement states of optical beams resonant with D1 line of Rubidium atoms at 795 nm. In this paper, We present the experimental generation of single-frequency high power 397.5 nm ultra-violet (UV) laser with long lifetime and perfect beam quality by using periodically poled MgO-doped stoichiometric lithium tantalate (MgO:PPSLT) crystal as the frequency doubler in an external enhancement ring cavity. When the transmission of the input coupler is 5.5%, the maximal output power of single-frequency 397.5 nm UV laser of 407 mW is obtained under the incident pump power of 1.9 W with the corresponding conversion efficiency of 22.8%. When the output power is 290 mW, the measured power stability and the beam quality are lower than 0.28% and 1.02, respectively. Moreover, any damage is not observed in our experiment which lasts about 1 year.

Power scaling of single-longitudinal-mode Nd:GdVO4 laser at 1342 nm

To scale the output power of a continuous wave Nd:GdVO4 laser at 1342 nm of a single-longitudinal-mode operation, a composite Nd:GdVO4 laser rod was employed and the cross section dimensions parameter of a laser crystal was optimized, the maximum single-frequency output power was 4.6 W. The stability of output power was better than ±1% in the given two hours.

Single Frequency LD-Pumped 2.09 μm Cr, Tm, Ho: YAG Microchip Laser

Single-frequency microchip lasers have been widely used in differential absorption radars, pulse coherent Doppler radars, pumping optical parametric oscillators, and etc. So theoretical analysis and experimental researches on the LD-pumped 2.09 μm microchip laser have important realistic meaning. According to quasi-three-level Cr, Tm, Ho: YAG(CTH:YAG) laser crystal working characteristics, the theoretical expression and relationship curve between the output optical power and 785nm LD-pumped power are obtained by theoretical calculating based on the pumping rate equation. The CTH:YAG crystal with 4mm diameter and 1 mm thickness is used to do experimental test. The corresponding three kinds of particle concentration are 0.85%, 5.9% and 0.36% respectively. When the crystal temperature is controlled at 10 °C, microchip laser beam output characteristic curve is obtained under different pump spots. The results show that when the pump spot diameter is 75um the maximum single-frequency output power is 32mW and when the pump beam is 100um the maximum single-frequency output power is 30mW. The corresponding optical to optical conversion slope efficiencies are 6.8% and 6% respectively.

Co-seeded Er3+:Yb3+ single frequency fiber amplifier with 60 W output power and over 90% TEM(00) content.

We report on the design and fabrication of an Er(3+):Yb(3+) triple clad fiber and on the power scaling of a single frequency fiber amplifier at 1.5 μm based on that fiber. In addition, we report on mode content measurements in order to reveal the overlap of the amplifier output with the TEM(00) mode. The triple clad design was used to enable high output power levels, a good slope efficiency and an excellent beam quality. A maximum single frequency output power of 61 W at 1.5 μm could be achieved with the aid of the co-seeding method, which was used to suppress parasitic processes at 1.0 μm. With a scanning ring cavity the mode content of the amplifier output was analyzed with respect to the TEM modes. For all output power levels the TEM(00) content was above 90%.

Optical noise of stabilized high-power single frequency optically pumped semiconductor laser

We present a study of an actively stabilized optically pumped semiconductor laser operating single frequency at a wavelength of 1015nm. In free running operation, the laser exhibits a single frequency output power of 15W with a linewidth of 995kHz for a sampling time of 1s. The intensity and the frequency of the laser were independently stabilized to reach a laser linewidth of only 4kHz for the same sampling time. To identify and reduce the different sources of noise, the relative intensity noise and frequency noise spectral density are investigated under various conditions.

Diode-end-pumped continuously tunable single frequency Tm, Ho:LLF laser at 206 μm

We report on a laser diode-end-pumped continuously tunable single frequency Tm, Ho:LLF laser near room temperature. For transmission of 5%, the maximum single frequency output power of 221 mW at 2064.4 nm was obtained by using two uncoated etalons. The single frequency Tm, Ho:LLF laser operated on the fundamental transverse mode with an M2 factor of 1.13, and the output frequency could be tuned continuously near 1.5 GHz by angle tuning only of the 1 mm thick etalon. Furthermore, the influence of output coupler transmission on the laser performance was also investigated. The single frequency laser can be used as a seed laser for coherent Doppler lidar and differential absorption lidar systems.

Modal instability-suppressing, single-frequency photonic crystal fiber amplifier with 811 W output power

An acoustic- and gain-tailored Yb-doped polarization-maintaining photonic crystal fiber is used to demonstrate 811 W single-frequency output power with near diffraction-limited beam quality. The fiber core is composed of 7 individually doped segments arranged to create three distinct transverse acoustic regions; including one region that is Yb-free. The utility of the Yb-free region is to reduce coupling between the LP01 and LP11 modes to mitigate the modal instability. The application of thermal gradients is utilized in conjunction with the transverse acoustic tailoring to suppress stimulated Brillouin scattering. To the best of our knowledge, the 811 W output represents the highest power ever reported from a near diffraction-limited single-frequency fiber laser.

A room temperature diode-pumped single frequency Er:YAG laser at 1645 nm

We report on p-polarized single-longitudinal-mode (SLM) operation of an Er:YAG laser at 1645.3 nm pumped by a laser diode at room temperature with three inserted Fabry–Perot etalons. An incident absorbed power of 6 W was used to generate the maximum single frequency output power of 75 mW. This stable SLM oscillation is encouraging since it may be used as a master laser for an injection-locked system.

A single longitudinal mode Tm, Ho:YLF laser with a continuously tunable frequency of 2.1 GHz with double F–P etalons

A diode-end-pumped single-frequency Tm (5%), Ho (0.5%):YLF laser is reported. At room temperature, the maximum single longitudinal mode (SLM) output power of 83 mW at a wavelength of 2068.7 nm was obtained, corresponding to a slope efficiency of 5.57%. The beam quality M2 of 1.73 was measured at the maximum single-frequency output power. The output frequency of the SLM Tm, Ho:YLF laser can be tuned continuously over 2.1 GHz.

Resonantly pumped monolithic nonplanar Ho:YAG ring laser with high-power single-frequency laser output at 2122 nm

We demonstrated a stable single-frequency laser operating at 2122 nm from a monolithic nonplanar Ho:YAG ring oscillator (NPRO). The Ho:YAG NPRO was resonantly pumped by a 1907 nm Tm:YLF laser built up by ourselves. The maximum multimode output power from the Ho:YAG NPRO was 9.66 W and the slope efficiency was 71.7%. With accurate adjustment of the pump position to make the laser oscillate in single frequency condition, an output power of 8.0 W was obtained with a slope efficiency of 61.4% and an optical-optical efficiency of 50.0%. The power stability of the Ho:YAG NPRO laser was 0.29% at maximum single frequency output power. The beam quality M(2) factors were measured to be less than 1.1 in x- and y- directions.