Output Wavelength Tuning Research Articles

Low-noise short-wavelength pumped frequency downconversion for quantum frequency converters

We present a highly efficient low-noise quantum frequency converter from the visible range to telecom wavelengths, combining a pump laser at intermediate frequency resonantly enhanced in an actively stabilized cavity with a monocrystalline bulk crystal. A demonstrator for photons emitted by nitrogen-vacancy-center qubits achieves 43% external efficiency with a noise photon rate per wavelength (frequency) band of 2 s−1/pm(17 s−1/GHz) – reducing the noise by two orders of magnitude compared with current devices based on periodically poled crystals with waveguides. With its tunable output wavelength, this device enables the generation of indistinguishable telecom photons from different network nodes and is, as such, a crucial component for a future quantum internet based on optical fiber.

Methods of Radiation Wavelength Tuning in Short-Pulsed Fibre Lasers

Methods of output wavelength tuning in short-pulsed fibre lasers are analysed. Many of them rely on spectral selection principles long used in other types of lasers. For compatibility with the fibre-optical format, the corresponding elements are sealed in compact, airtight volumes with fibre-optical radiation input and output. A conclusion is presented about the relatively small number of inherently “fibre-optical” ways of tuning the wavelength of radiation. It is demonstrated that the range of output wavelength tuning in short-pulsed fibre lasers may span hundreds of nanometres (even without extension beyond the active medium gain contour through nonlinear effects). From the presented review results, it may be concluded that the search for the optimal tuning method complying with the user-preferred all-PM-fibre short-pulsed laser design is not yet complete.

Plasmonic structure assisted all-optical tunable fiber laser

In this paper, we proposed and demonstrated a tunable fiber laser using all-optical plasmonic modulation, where the localized surface plasmon resonance effect of gold nanobipyramids (GNBPs) and polarization maintaining thin-cladding photonic crystal fiber were utilized to realize tunable output wavelength controlled by the 980 nm pump light. The laser achieves a tunability of 2.21 nm in C-band, with a side mode suppression ratio of 27 dB and the peak intensity can also be tuned continuously. The proposed tunable laser shows an average power fluctuation of less than 1 dB and the output wavelength and the power intensity both exhibit high stability. Therefore, the proposed plasmonic structure assisted all-optical tunable laser has advantages such as compact structure, good reproducibility, continuous tuning, and simple operation, which indicates great potential in future all-optical applications.

1.8-µm laser operation based on femtosecond-laser direct written Tm:YVO4 cladding waveguides.

In this work, we have demonstrated tunable 1.8-µm laser operation based on a Tm:YVO4 cladding waveguide fabricated by means of femtosecond laser direct writing. Benefiting from the good optical confinement of the fabricated waveguide, efficient thulium laser operation, with a maximum slope efficiency of 36%, a minimum lasing threshold of 176.8 mW, and a tunable output wavelength from 1804 to 1830nm, has been achieved in a compact package via adjusting and optimizing the pump and resonant conditions of the waveguide laser design. The lasing performance using output couplers with different reflectivity has been well studied in detail. In particular, due to the good optical confinement and relatively high optical gain of the waveguide design, efficient lasing can be obtained even without using any cavity mirrors, thereby opening up new possibilities for compact and integrated mid-infrared laser sources.

Stable wavelength-swept single-frequency erbium fiber laser in L-band tuning bandwidth

In the study, we demonstrate an erbium-doped fiber (EDF) laser system by integrating the Mach–Zehnder interferometer (MZI) and triple-fiber-ring structures to generate the single-longitudinal-mode (SLM) output in L-band bandwidth. Here, a sub-ring with a 5.5 m unpumped EDF based saturable absorber (SA) is also applied to induce the narrowband auto-tracking filter behavior. Based on the proposed fiber cavity induced mode-filter effect, the EDF laser can achieve the stable, narrow and wavelength-tunable output characteristics over an effective tuning range of 1568.0 to 1613.0 nm. Furthermore, the output stability, optical signal to noise ratio (OSNR), output power and laser linewidth of the laser are also performed and discussed.

All-solid-state far-UVC pulse laser at 222 nm wavelength for UVC disinfection

A 222 nm all-solid-state far-ultraviolet C (UVC) pulse laser system based on an optical parametric oscillator (OPO) and second-harmonic generation (SHG) using β-Ba2BO4 (BBO) crystals was demonstrated. Pumped by a Nd:Y3Al5O12 laser with a repetition rate of 100 Hz at 355 nm, the maximum signal laser pulse energy of 1.22 mJ at 444 nm wavelength was obtained from the BBO-OPO system, corresponding to a conversion efficiency of 27.9%. The maximum output pulse energy of 164.9 µJ at the 222 nm wavelength was successfully achieved, corresponding to an SHG conversion efficiency of 16.2%. Moreover, the tunable output wavelength of UVC light from 210 nm to 252.5 nm was achieved.

Single-longitudinal-mode short-cavity Brillouin random fiber laser via frequency auto-tracking with unpumped-EDF sagnac loop

A single-longitudinal-mode high-coherence Brillouin random fiber laser (BRFL) with low-noise and narrow linewidth is proposed and experimentally demonstrated, which owns the shortest cavity structure ever reported in BRFL configuration by the combined utilization of highly nonlinear fiber (HNLF) and unpumped Er-doped-fiber sagnac loop (UESL). In this BRFL, stimulated Brillouin scattering and Rayleigh scattering are exploited to provide the resonant gain and random distributed feedback, respectively. The UESL, with a narrow bandpass width and a capability of auto-tracking the center frequency of the transmitted light, is realized by forming a dynamic fiber grating (DFG) filter with periodically modulated refractive index through the saturable absorption effect and hole-burning effect along the Er-doped fiber. The UESL can effectively act as a center-frequency-auto-tracking bandpass filter with narrow bandwidth to filter out the undesired dense random modes and simultaneously restrict the resonant modes within a very limited frequency range. It thus suppresses the modes hopping and multi-mode resonances within the Brillouin gain bandwidth so that the frequency jitter and instability of laser output are greatly alleviated. The short cavity was realized by utilizing a section of HNLF with high nonlinearity coefficient (≥10 W−1·km−1 @1550 nm), which can provide enough Brillouin gain for the BRFL when short length is employed. Compared with the currently prevalent BRFLs based on long-cavity configurations, the short-cavity structure enables a significant reduction in the number of random cavity modes so as to guarantee a high probability for the single-longitudinal-mode random lasing output. In the experiment, a stable single-longitudinal-mode lasing output with an ultra-narrow linewidth of ∼802.42 Hz is obtained from the proposed BRFL. Statistical characteristics of the mode resonances, laser noise performance and statistical analysis of the lasing output are also experimentally investigated for the proposed BRFL. In addition, broadband wavelength-tunable output is realized in the proposed BRFL.

Compact wavelength tunable output around 440 nm pulsed laser for oceanic lidar application

A single-resonant BBO-based optical parametric oscillator (OPO) with 27 nm tuning range in deep-blue spectral band around 440 nm was developed. Pumped by a 355 nm ultraviolet laser with 4.9 mJ pulse energy at 100 Hz repetition rate, maximum pulse energy of 1.32 mJ at 441.4 nm wavelength, corresponding to more than 0.26 MW peak power, was successfully obtained from a plano-concave OPO cavity with an about 35% output coupler, the optical–optical​ conversion efficiency was up to 26.9%. The pulse width was around 5.0 ns, and the spectral linewidth was about 0.09 nm. When the output wavelength was tuned to the Fraunhofer lines of 440.5 nm and 438.4 nm, the pulse energy of 1.27 mJ and 1.15 mJ was obtained respectively with linewidth of both about 0.07 nm, well-matched to the corresponding Fraunhofer linewidth.

Q-switched tunable fiber laser with aluminum oxide saturable absorber and Sagnac loop mirror

A Q-switched erbium-doped fiber laser with tunable output wavelength was demonstrated by utilizing aluminum oxide saturable absorber in conjunction with Sagnac loop mirror (SLM) filter. As the SLM temperature was increased from 30 to 70 °C, the laser operation can be tuned from 1568 to 1556 nm. At 1568 nm operation, the laser pulse frequency can be raised from 13.66 to 26.25 kHz by increasing the pump power from the threshold of 53 to 87 mW. With the increase in temperature, it is found that the pump threshold for the Q-switching increased, while the laser operation shifted to a shorter wavelength.

Q-switched and tunable wavelength fiber laser utilizing nickel oxide saturable absorber and sagnac loop mirror filter

We demonstrate a Q-switched Erbium-doped fiber laser (EDFL) with a tunable output wavelength using Nickel oxide (NiO) saturable absorber (SA) in conjunction with a Sagnac loop mirror (SLM) filter. The proposed SA was prepared by embedding NiO nanoparticles obtained bysimplistic sonochemical reaction into polyethylene oxide (PEO). The NiO PEO film was integrated into a figure-of-eight resonator configured with a SLM to generate Q-switched pulses with a tunable output wavelength. As the SLM temperature was increased from 30 °C to 70 °C, the laser operation can be tuned from 1551.9 nm to 1544.1 nm. At 1551.9 nm operation, the repetition rate rose from 36.2 kHz to 40.3 kHz and the pulse duration reduced from 10.00 to 9.32 μs when the pump power rose from 131.5 to 161.0 mW. At the highest pump power of 161.0 mW, the maximum output power and pulse energy were obtained at 0.67 mW and 16.6 nJ. For Q-switched operation at 1544.1 nm, the produced Q-switched pulse exhibited a pulse duration of 8.88 μs, the repetition rate of 45.7 kHz, the highest output power of 0.60 mW and pulse energy of 13.1 nJ at the maximum pump power of 161.0 mW.

Measurement of differential modal group delay of a few-mode fiber using a Fourier domain mode-locked laser

We propose and experimentally demonstrate a method for measuring the differential modal group delay (DMGD) of a few-mode fiber using a Fourier domain mode-locked laser (FDML). We use the fast frequency-swept, wavelength-tunable output of the FDML in order to perform time domain measurements of interference of the modes, which is further postprocessed to extract the DMGD. We demonstrate the measurement of DMGD for a commercial two-mode fiber over the C-band. This method is not limited by the magnitude of DMGD or the number of modes and is minimally affected by time-dependent polarization and mode fluctuations, environmental noise, and spectral resolution of instruments.

Graphene-PVA saturable absorber for generation of a wavelength-tunable passively Q-switched thulium-doped fiber laser in 2.0 µm

Graphene, a 2D material, has been used for generation of pulse lasers due to the presence of its various fascinating optical properties compared to other materials. Hence in this paper, we report the first demonstration of a thulium doped fiber laser with a wavelength-tunable, passive Q-switched output using a graphene-polyvinyl-alcohol composite film for operation in the 2.0 µm region. The proposed laser has a wavelength-tunable output spanning from 1932.0 nm to 1946.0 nm, giving a total tuning range of 14.0 nm. The generated pulse has a maximum repetition rate and average output power of 36.29 kHz and 0.394 mW at the maximum pump power of 130.87 mW, as well as a pulse width of 6.8 µs at this pump power. The generated pulses have a stable output, having a signal-to-noise ratio of 31.75 dB, and the laser output is stable when tested over a period of 60 min. The proposed laser would have multiple applications for operation near the 2.0 micron region, especially for bio-medical applications and range-finding.

Passively mode-locked 354–1200 fs and continuous-wave 1044–1081 nm tunable operation of diode-pumped Nd,La:SrF2 laser

The fundamental spectroscopic properties of four Nd,La:SrF2 crystals with different and concentrations are described. The laser generation was successfully achieved with all crystals; the best results with the at.% , 8 at.% : are presented. The laser output wavelength tuning properties were investigated, and were found to have continuous tuning range over 37 nm from 1044 to 1081 nm. Two different saturable absorbers were succesfully tested for the passively mode-locked regime, and the intracavity dispersion compensation influence was studied. In the optimal set-up, a continuously mode-locked train of pulses as short as 354 fs was generated at the repetition rate of MHz. The laser central wavelength was ∼1059 nm and the overall output power reached 300 mW in two beams with absorbed pump power of less than W.

Compact resonantly intra-cavity pumped tunable Ho:Sc2SiO5 laser

A compact intra-cavity pumped low threshold continuous-wave Ho:Sc2SiO5 laser is reported. The characteristics of output wavelength tuning are investigated by use a intra-cavity briefringent (BF) filter. A wavelength tunable range of 140nm from 2020 to 2160nm is achieved. For the free-running mode, the laser slope efficiency is 24.8%, when the output central wavelength is 2110nm. The laser threshold is about 820mW of incident pump power. With the BF filter, a maximum output power of 870mW is obtained at the incident pump power of 5W, corresponding to a slope efficiency of 20.3%. The characteristics of output wavelength verse the crystal temperature are also investigated.

A continuous-wave wide-tunable Ho:Sc2SiO5 laser between 2.05 and 2.16 μm

A widely tunable Holmium-doped Sc2SiO5(SSO) 2 μm laser is reported in this manuscript, which has a wavelength tunable range of 110 nm (from 2050 to 2160 nm). A maximum output power of 3.02 W at 2111 nm is obtained when the laser operates on the continuous-wave free-running mode. A birefringent filter is used to realize the output wavelength tuning, which is put into the laser resonant cavity. The maximum output power of the tunable Ho:SSO laser is 2.07 W. It is the first time to report a widely tunable Ho:SSO laser. The wavelength tunable range is wider than the ones of other Ho-doped lasers and the output power is higher too, which could extend application fields of the Ho-doped lasers.

20-W Wavelength-Tunable Picosecond Yb-Doped Fiber MOPA Source Seeded by an NPR Mode-Locked Fiber Laser

We demonstrated a high-power wavelength-tunable picosecond Yb-doped fiber master oscillator power amplifier source without any tunable elements for the first time. This wavelength-tunable output was realized based on the birefringence-induced filter effect of the nonlinear polarization rotation mode-locked fiber laser, which worked as the seed source. Through cascaded single-mode Yb-doped fiber preamplifiers together with two double-cladding Yb-doped fiber amplifiers, the pulses were amplified up to 21.2-W output power in the wavelength range from 1038.4 to 1060 nm with a pulse duration of 9.5 ps, an optical signal-to-noise ratio of 25 dB, and a beam quality M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 1.16 at the repetition rate of 178 MHz.

Tunable single frequency microchip Nd:YAP MOPA laser operating at 1.08 μm

A longitudinally laser diode (LD)-pumped Nd:YAP microchip master oscillator power amplifier (MOPA) system operating at 1.08 μm was demonstrated. The system consisted of a longitudinally LD-pumped monolithic Nd:YAP microchip master laser and a two-stage disc amplifier. The cavity length of the master oscillator was 500 μm. The short cavity length lead to a large frequency separation between the resonator modes and hence single longitudinal mode operation was achieved. Pumped by a high-brightness LD an output power of 155 mW in both single longitudinal and transverse mode was generated. To scale to a high power, the output power from the master oscillator was amplified by amplifier discs. The amplified output power was 1.43 W. The central wavelength of the laser system was tuned by changing the cavity length and refractive index via temperature. Using a shorter master oscillator (L = 310 μm) a continuous output wavelength tuning over the gain profile of 0.9 nm was realized. To our knowledge this is the first study of a MOPA system based on an LD-pumped microchip Nd:YAP laser.

Continuous-wave mid-infrared intra-cavity singly resonant PPLN-OPO under 880 nm in-band pumping

We report herein a continuous-wave mid-infrared intra-cavity singly resonant optical parametric oscillator (ICSRO) which is the first example of ICSRO that utilize in-band pumped Nd-doped vanadate laser as pump source. A 1064 nm Nd:YVO₄ laser in-band pumped by 880 nm LD and a periodically poled lithium niobate (PPLN) crystal are employed as the parent pump laser and the nonlinear medium, respectively. The idler output wavelength tuning range is 3.66-4.22 µm. A maximum output power of 1.54 W at 3.66 µm is obtained at absorbed pump power of 21.9 W, with corresponding optical efficiency being 7.0%. The control experiment of ICSRO under 808 nm traditional pumping is also carried out. The results show that in-band pumped ICSRO has better performance in terms of threshold, power scaling, efficiency and power stability than ICSRO traditionally pumped at 808 nm.

Three-dimensional numerical investigations of the laser-beam interactions in an undulator

Laser-beam interaction in an undulator is commonly suggested in the development of free electron laser (FEL) schemes. In this paper, a three-dimensional algorithm is developed to assist in laser-beam interaction simulation in an undulator, which is built on the basis of the fundamentals of electrodynamics, i.e. the electron's behavior is determined by the magnetic field and the laser electric field in the time domain. On the basis of the algorithm, the detuning effect in a laser heater, the carrier envelope phase effect of a few-cycle laser in attosecond X-ray FEL schemes and output wavelength tuning in a high gain harmonic generation FEL are numerically discussed.

All-optical wavelength multicasting exploiting cross-phase modulation in a dispersion-flattened nonlinear photonic crystal fiber

An all-optical wavelength multicasting scheme with tunable output wavelength and channel numbers has been proposed and demonstrated based on cross-phase modulation (XPM) in a dispersion-flattened highly nonlinear photonic crystal fiber. We show that the input signal wavelength can be simultaneously converted to four different wavelengths by filtering the broadened sideband of the continuous-wave (CW) probe beams. The experiments are carried out to investigate into the wavelength tunability, and exploit the dynamic characteristics with variable input signal powers, the ability of multicasting channels scalable, and the relationship between the multicasting signal qualities with variable optical band-pass filter (OBPF) bandwidth. The results indicate that the proposed wavelength multicasting scheme has the advantages of simple structure, efficient operation in a wide wavelength range, as well as transparent to bit rates. Moreover, the system can be upgraded to generate more multicasting channels by increasing the number of CW probe beams.