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Ytterbium-Doped Fiber Amplifiers (YDFA), 1 µm
Single Mode YDFA
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This plot gives the output power as a function of input power for our polarization-maintaining YDFAs. A complete set of performance graphs is available on the Graphs tab.
Thorlabs' Core-Pumped Ytterbium-Doped Fiber Amplifiers (YDFAs) offer 20 dBm (100 mW) typical output power with a low noise figure of <8 dB. Each is enclosed in a compact, turnkey benchtop package with FC/APC input and output connectors. In order to support applications involving femtosecond pulses, they are engineered to impart minimal dispersion. Each YDFA includes built-in input and output isolators to minimize back reflections to the amplifier and light source. Custom amplifiers with higher output power and gain is also available upon request; please contact firstname.lastname@example.org with inquiries.
Versions for single mode or polarization-maintaining operation are available. The YDFA100S uses HI1060 single mode fiber with <0.3 dB polarization-dependent gain. The YDFA100P is a polarization-maintaining amplifier with input and output isolators that block light polarized along the fast axis of the PM980-XP fiber. Therefore, the YDFA100P is designed to work with input signals polarized along the slow axis of the fiber. Output light from the amplifier has a polarization extinction ratio of >20 dB. The input and output fiber connector keys are aligned to the slow axis of the fiber.
The pump current of the ytterbium-doped fiber amplifier is adjustable through the instrument's front panel, allowing the user to vary the gain and output power of the amplifier. In addition, remote control of the pump current is supported by sending serial commands via a USB 2.0 connector. For added safety, the user may connect an interlock circuit to the 2.5 mm mono jack on the rear panel.
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YDFA100P Front Panel
The front panel of the YDFAs include a digital display, a rotating knob that adjusts the pump laser current, a key switch, and an amplifier enable switch button paired with a green LED.
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YDFA100P Back Panel
The back panel of the YDFAs include a USB type B connector for remote operation and a 2.5 mm mono jack for a user-designed interlock circuit.
Unless otherwise indicated, all values are specified for a CW input beam at 1050 nm.
Unless otherwise stated, all performance graphs below were obtained using a CW input, the maximum pump current of 1000 mA, and the factory pump temperature setting of 25 °C. Performance may vary from unit to unit; this data reflects the typical performance of our YDFAs, and is presented for reference only. The guaranteed specifications are shown in the Specs tab.
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The typical gain as a function of the wavelength. The blue-shaded region denotes the specified operating wavelength range.
Femtosecond Pulse Amplification
Ultrafast pulses amplified by a YDFA will experience some pulse broadening due to dispersion effects. This dispersion is a natural consequence of light moving through the doped gain fiber and other fiber components and cannot be eliminated completely. Thorlabs' YDFA amplifiers optimize the gain fiber length to minimize dispersion and nonlinearity while maximizing the amplification gain. After amplification, the pulse can be compressed to attain a pulse width closer to the input pulse. The fibers used in the YDFA100P and YDFA100S have identical dispersion and nonlinearity and thus can both be used in femtosecond applications.
Simulated results of amplification for three different input pulses through the YDFA100P amplifier are shown in the graphs below and the table to the right. The input pulses are specified at 1045 nm and 26 pJ pulse energy, and with a 50 fs, 100 fs, or 200 fs pulse width. The YDFA amplifier simulations set the gain at 1045 nm to 17.1 dB and use the measured gain spectral shape in calculating the amplified pulse. In addition, the YDFA is modeled with 1 m of polarization-maintaining fiber before and after the amplifier. Finally, the results below also show simulated pulse compression of the post-amplification pulse using a pair of 1200 lines/mm diffraction gratings. Optical loss in the grating pair has been neglected for the calculation of the peak power values shown in the table.
Experimental Validation of YDFA100P Amplification
This experiment combines measurement of an amplified pulse in the YDFA100P with numerical simulation of the expected output pulse. A 117 fs input pulse was generated using a 100 MHz oscillator. The YDFA100P was used to amplify the pulse from a 2.6 mW average power to 140 mW, and then the output pulses were compressed using an external pulse compressor. The input and output pulse intensity profiles were characterized using frequency-resolved optical gating (FROG) measurements.
The results shown below indicate that the amplified pulses were compressible to their original width due to the low nonlinearity and third-order dispersion effects in the YDFA. Simulations of the input and output pulse using the model discussed above are also shown alongside the experimental data and show relative agreement with the experimental results. The fibers used in the YDFA100P and YDFA100S have identical dispersion and nonlinearity and thus can both be used in femtosecond applications.
Fiber amplifiers such as EDFAs and YDFAs are typically better suited than semiconductor optical amplifiers (e.g., BOAs and SOAs) for amplifying femtosecond laser pulses. These amplifier types differ in their saturation energies, their gain saturation dynamics, and their free carrier lifetimes. In semiconductor amplifiers, the saturation energies are relatively low, on the order of a few picojoules. This limits the amplified pulse energy that can be achieved by semiconductor amplifiers. By way of comparison, in fiber amplifiers, the saturation energies exceed microjoule levels. Additionally, the gain recovery times in semiconductor amplifiers are governed by the carrier lifetime, which is in the 10 ps to 100 ps timescale. The carrier lifetime of fiber amplifiers is typically in the 10 µs to 1 ms timescale.
The YDFA100S and YDFA100P contain the following components: