Residual Pump Research Articles

Simultaneous 08, 10, and 13 μm multispectral and common-path broadband source for optical coherence tomography

Simultaneous multispectral generation in 0.8, 1.0, and 1.3 μm wavelength ranges by efficient energy conversions of 1.0 μm wavelength femtosecond pulses through a nonlinear fiber was reported. The output spectral range of this multispectral light source was composed of 0.6-0.9 μm blue-shifted Cherenkov radiation (CR), 1.0 μm residual pump, and 1.1-1.7 μm red-shifted soliton self-frequency shift (SSFS) with more than 1 mW/nm power-spectral densities. Output characteristics of the multispectral light source were then quantitatively analyzed and the central wavelengths of CR and SSFS emissions can be further easily adjusted by changing the input power into wavelength conversion fiber. Example spectral-domain optical coherence tomography (OCT) images of an IR card and finger skin were also performed with the demonstrated source. Due to the advantages of its simplicity, easily operated, and wavelength tunability, the reported multispectral source could be widely applicable for various spectroscopic OCT applications.

Numerical Investigation of Periodically Unsteady Pressure Field in a High Power Centrifugal Diffuser Pump

Pressure fluctuations are the main factors that can give rise to reliability problems in centrifugal pumps. The periodically unsteady pressure characteristics caused by rotor-stator interaction have been investigated by CFD calculation in a residual heat removal pump. Side chamber flow effect is also considered for the simulation to accurately predict the flow in whole flow passage. The pressure fluctuation results in time and frequency domains were considered for several typical monitoring points in impeller and diffuser channels. In addition, the pressure fluctuation intensity coefficient (PFIC) based on standard deviation was defined on each grid node for entire space and impeller revolution period. The results show that strong pressure fluctuation intensity can be found in the gap between impeller and diffuser. As a source, the fluctuation can spread to the upstream and downstream flow channels as well as the side chamber channels. Meanwhile, strong pressure fluctuation intensity can be found in the discharge tube of the circular casing. In addition, the obvious influence of operational flow rate on the PFIC distribution can be found. The analysis indicates that the pressure fluctuations in the aspects of both frequency and intensity can be used to comprehensively evaluate the unsteady pressure characteristics in centrifugal pumps.

Efficient and broadband Stokes wave generation by degenerate four-wave mixing at the mid-infrared wavelength in a silica photonic crystal fiber

Based on degenerate four-wave mixing (FWM), the broadband Stokes waves are efficiently generated at the mid-infrared wavelength above 2 μm, for the first time to our knowledge, by coupling the femtosecond pulses into the fundamental mode of a silica photonic crystal fiber designed and fabricated in our laboratory. Influences of the power and wavelength of pump pulses on the phase-matched frequency conversion process are discussed. When pump pulses with central wavelength of 815 nm and average power of 300 mW are used, the output power ratio of the Stokes wave generated at 2226 nm and the residual pump wave P(s)/P(res) is estimated to be 10.8:1, and the corresponding conversion efficiency η(s) and bandwidth B(s) of the Stokes wave can be up to 26% and 33 nm, respectively. The efficient and broadband Stokes waves can be used as the ultrashort pulse sources for mid-infrared photonics and spectroscopy.

Broadband Plasmonic Absorber for Photonic Integrated Circuits

Surface plasmon polaritons losses have long been considered as a fatal shortcoming of plasmonics based information transport. Here, we propose a plasmonic absorber utilizing this shortcoming to absorb the stray light in photonic integrated circuits (PICs). Benefiting from adiabatic mode evolution, its performance is insensitive to incident wavelength with bandwidth larger than 300 nm, and is robust against surrounding environment and temperature. Besides, the use of metal enables it to be very compact and beneficial to thermal dissipation. With this 40-\(\mu \) m-long absorber, the absorption efficiency can be over 99.8% at 1550 nm, with both the reflectivity and transmittance reduced to <;0.1%. Such a device may find various applications in PICs, to eliminate the residual strong pump laser or stray light.

A tunable dual-wavelength pump source based on simulated polariton scattering for terahertz-wave generation

We propose a dual-wavelength pump source by utilizing stimulated polariton scattering in a LiNbO3 crystal. The residual pump and the generated tunable Stokes waves can be combined to generate THz-wave generation via difference frequency generation (DFG). With a pump energy of 49 mJ, Stokes waves with a tuning range from 1067.8 to 1074 nm have been generated, and an output energy of up to 14.9 mJ at 1070 nm has been achieved with a conversion efficiency of 21.7%. A sum frequency generation experiment was carried out to demonstrate the feasibility of the proposed scheme for THz-wave DFG.

Theoretical and experimental study of multifunction C+L band hybrid fiber amplifiers

Abstract We proposed and demonstrated a 100 km hybrid C+L band fiber amplifier in the bridge-type scheme. It is composed of a C-band erbium-doped fiber amplifier (EDFA) and an L-band Raman fiber amplifier (RFA) using double-pass dispersion compensators in a loop-back scheme. Dispersion slope mismatch is compensated precisely for all C+L band channels by writing fiber Bragg gratings (FBGs) at appropriate locations. Gain variation among multiple channels can be reduced to ±0.2 dB. The pump efficiency is improved by recycling the residual pump power. The C/L band WDM coupler which at merged point rejects C band amplified spontaneous emission (ASE) using L band coupler and vice versa. Both the simulation results and experimental measurements are realized in this paper. The hybrid EDFA/RFA may find vast applications in WDM long-haul systems and optical networks.

Processing residual pump blood using ultrafiltration during cardiovascular surgery

Processing residual pump blood using ultrafiltration during cardiovascular surgery

Processed residual pump blood using ultrafiltration during cardiovascular surgery

Processed residual pump blood using ultrafiltration during cardiovascular surgery

WDM PON purpose remote pumped bidirectional EDFA using cascading FBGS as a pump reflector

ABSTRACTWe proposed a remote pumped bidirectional C+L band fiber amplifier for wavelength division multiplexing passive optical network. A high‐reflectivity pump reflector using three cascading fiber Bragg gratings is designed to reflect the residual pump power for L‐band amplification. Both the gains for C‐band and L‐band are larger than 10.0 dB under −10 dBm launched power. Using the remote pumped bidirectional fiber amplifier, the power penalty is only 0.82 dB after 10 Gb/s, 24 km bidirectional transmission. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2553–2556, 2013

Novel Technique for Obtaining the Raman Gain Efficiency of Silica Fibers

We present a simple novel technique that determines with precision the Raman gain efficiency for telecom fibers. The method is supported by a mathematical relation, which is the solution for the coupled differential equations that govern the stimulated Raman scattering. This technique is valuable due to its simplicity and consists of measuring the residual pump and the Raman scattering signals at the stimulated Raman scattering threshold. Our technique was proven for different fibers; as a result, we found that the rate of pump power to stimulated Raman scattering at threshold is lower than 16, which is the historically used value.

Influence of a bidirectional recycling residual pump on the Stokes signal characteristics of a linear cavity Brillouin fiber laser

The effect of a bidirectional recycling residual pump on the Brillouin Stokes signal threshold, as well as on its power, is experimentally investigated. The laser cavity is formed with two optical mirrors as the resonator reflectors which allow bidirectional residual pump recycling that causes bidirectional Brillouin gains. These gains significantly reduce the threshold power and increase the Stokes signal power. For the same single mode fiber length, the Brillouin Stokes signal threshold is reduced by up to 75% and 50% in the laser structure compared to its values in conventional and recycling Brillouin threshold reduction techniques, respectively. In addition, the effect of Brillouin gains on the Stokes signal power is illustrated and exhibits no additional gain in the laser cavity as compared with the recycling technique, especially for long fibers >8 km.

Long distance fiber Bragg grating strain sensor interrogation using a high speed Raman-based Fourier domain mode-locked fiber laser with recycled residual Raman pump

We propose a novel fiber Bragg grating (FBG) sensor interrogation using a Raman-based Fourier-domain mode locking (FDML) fiber laser for a high speed and long distance measurement. A residual Raman pump after the generation of the Raman-based FDML fiber laser is recycled for secondary signal amplification in a 2-m erbium-doped fiber (EDF) to further enhance the output power. The chromatic dispersion is precisely controlled to suppress the phase noise in the FDML laser cavity, resulting in the improvement of an R-number of 1.43 mm/dB. After recycling residual pump, we achieve the 40-km round trip transmission of the sensing probe signal with a high scan rate of 30.8 kHz. With 205-mW residual pump power, the bandwidth and the maximum gain are measured to be more than 50 nm, 10.3 dB at 1550 nm, respectively. The sensitivity of the proposed Raman-based FDML fiber laser to strain is also measured, which are 0.81 pm/μstrain in the spectral domain and 0.19 ns/μstrain in the time domain, respectively.

Electromagnetically induced transparency of single Λ-type three-level atoms in a high-finesse optical cavity

We study the features of electromagnetically induced transparency (EIT) in a single Λ-type three-level atom placed in a high-finesse cavity under the action of a coupling laser and a probe laser. Our calculations show that three transparency windows appear when the pump strength is large enough. This can be explained by the residual pump in the cavity mostly resulting in energy splitting. The level |3〉 is split into four slightly different energy levels, and interference takes place between the excitation pathways. Furthermore, it is also shown that the frequencies of the EIT windows can be tuned by changing the coupling field detuning Δ2, and that the reflection profile is very sensitive to the cavity field detuning Δc.

Efficient dual-wavelength laser at 946 and 1064 nm with compactly combined Nd:YAG and Nd:YVO4 crystals

We originally employ a compact combination of a Nd:YAG crystal and a Nd:YVO4 crystal to develop an efficient dual-wavelength laser operating at 946 and 1064 nm. We exploit a short Nd:YAG crystal to generate 946 nm laser by reducing the reabsorption loss and a follow-up Nd:YVO4 crystal to generate a 1064 nm laser by absorbing the residual pump light. The output power ratio between the 946 and 1064 nm emissions can be flexibly adjusted from 0.3 to 0.9 by varying the separation between the two output couplers. At an incident pump power of 17 W, the total output power is generally higher than 5.2 W, with an overall optical-to-optical efficiency greater than 30%.

Polarization-dependent efficient Cherenkov radiation at visible wavelengths in hollow-core photonic crystal fiber cladding

Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0° to 45°, the Raman soliton shifts from 2227 to 2300 nm, the output power of the CR increases 8.15 times, and the maximum output power ratio of the CR at 556 nm to the residual pump is estimated to be 20:1. The width of the output optical spectrum at visible wavelengths broadens from 25 to 45 nm, and the conversion efficiency of the CR can be above 28%. Moreover, the influences of the pump polarization and wavelength on the CR are studied, and the corresponding nonlinear processes are discussed.

An efficient, compact pulsed D2O terahertz super-radiant laser pumped with a fundamental transverse mode transversely excited atmospheric pressure CO2 laser

An efficient, compact pulsed D2O terahertz (THz) super-radiant laser pumped by a TEA (transversely excited atmospheric pressure) CO2 laser is presented. The pulse energy of the THz laser has been discussed as a function of CO2 laser pump energy, D2O gas pressure, and pump absorption. A pulse width of about 110 ns and the maximum pulse energy of about 1.3 mJ have been achieved at 385 μm, with pumping by a 378 mJ fundamental transverse mode TEA CO2 laser, and the photon conversion efficiency of 29% has been achieved. We have also studied the temporal behavior features such as the decay time, the full width at half-maximum, and the pulse broadening of the THz laser pulse compared with the pump pulse and the residual pump pulse at the optimum pressure.

Processed residual pump blood in cardiac surgery: the Processed Residual Blood in Cardiac surgery trial

Processing residual cardiopulmonary bypass (CPB) volume via ultrafiltration may improve hemostasis and reduce transfusion through clearing activated complement, activated coagulation components, and proinflammatory cytokines. We sought to establish if processing residual CPB volume with ultrafiltration reduces homologous blood transfusion and bleeding. Adult patients undergoing isolated coronary artery bypass grafting (CABG) surgery were randomly assigned to receive processed (n = 99) or unprocessed (control; n = 98) residual CPB volume in this single-center randomized controlled trial. The intensive care unit team, patients, and assessors were blinded to treatment assignment and a transfusion protocol was followed. Surgeons were permitted to use retrograde autologous priming to minimize crystalloid pump prime. The processed study bag was of a smaller volume (280 [0, 550] mL vs. 590 [215, 726] mL; p < 0.01) but a higher hematocrit (29% [0%, 34%] vs. 23% [20%, 25%]; p < 0.01) than control. The rate of transfusion with homologous blood was 39% in both groups (p = 0.92). There was no difference in the volume transfused (processed 323 ± 585 mL vs. control 276 ± 520 mL; p = 0.56). There was also no difference in the proportion of patients transfused with any blood product (processed 44% vs. control 45%; p = 0.95) or in the volume of chest tube output (processed 600 [500, 940] mL vs. control 670 [490, 932] mL; p = 0.62). Ultrafiltration of residual CPB volume in adults undergoing isolated CABG surgery does not reduce the need for transfusion or bleeding.

Highly efficient Cherenkov radiation generation in the irregular point of hollow-core photonic crystal fiber

Highly efficient Cherenkov radiation (CR) is generated by the soliton self-frequency shift (SSFS) in the irregular point of a hollow-core photonic crystal fiber (HC-PCF) in our laboratory. The impacts of pump power and wavelength on the CR are investigated, and the corresponding nonlinear processes are discussed. When the average power of the 120 fs pump pulse increases from 500 mW to 700 mW, the Raman soliton shifts from 2210 nm to 2360 nm, the output power of the CR increases by 2.3 times, the maximum output power ratio of the CR at 539 nm to that of the residual pump is calculated to be 24.32:1, the width of the output optical spectrum at the visible wavelength broadens from 35 nm to 62 nm, and the conversion efficiency η of the CR in the experiment can be above 32%.

Increased signals from short-wavelength-excited fluorescent molecules using sub-Ti:Sapphire wavelengths.

We report the use of an all-solid-state ultrashort pulsed source specifically for two-photon microscopy at wavelengths shorter than those of the conventional Ti:Sapphire laser. Our approach involves sum–frequency mixing of the output from an optical parametric oscillator (λ= 1400–1640 nm) synchronously pumped by a Yb-doped fibre laser (λ= 1064 nm), with the residual pump radiation. This generated an fs-pulsed output tunable in the red spectral region (λ= 620–636 nm, ∼150 mW, 405 fs, 80 MHz, M2∼ 1.3). We demonstrate the performance of our ultrashort pulsed system using fluorescently labelled and autofluorescent tissue, and compare with conventional Ti:Sapphire excitation. We observe a more than 3-fold increase in fluorescence signal intensity using our visible laser source in comparison with the Ti:Sapphire laser for two-photon excitation at equal illumination peak powers of 1.16 kW or less.

Method for stripping cladding light in the High power fiber laser

The output performance of large mode area (LMA) all-fiber laser are affected by the stripping ability of cladding light, which is consisting of the residual pump light and cladding mode signal light. The common method of stripping cladding light is to recoat the DCF (double clad fiber) with a high index gel, but it strips the cladding light quickly within the first few millimeters and makes the local temperature too high. In order to strip the power of cladding light uniformly over the length of the fiber, a method corroding the inner cladding layer to special shape is proposed. The Monte Carlo algorithm is used to simulate the performance of this method. The results show that it has the attenuation ability of 26dB and can strip the cladding light uniformly without making local temperature too high.