Feng Zhouming

Efficient Fibre Amplifiers Based on a Highly Er3+/Yb3+ Codoped Phosphate Glass-Fibre

Highly Er3+/Yb3+-codoped single-mode phosphate glass fibre is fabricated by the rod-in-tube technique. The performances of high-concentration Er3+/Yb3+-codoped phosphate glass fibre amplifiers are investigated and discussed. An efficient optical fibre amplifier with a gain of 12.6 dB based on a 3.0 cm long Er3+/Yb3+-codoped phosphate glass fibre is demonstrated under a dual-pump configuration with two 976 nm fibre-pigtail laser diodes, which make it attractive for compact Er3+ -doped fibre amplifiers. The obtained noise figures of signal wavelength from 1525 to 1565 nm are less than 6.0 dB. Gain saturation behaviour at 1535 nm is also investigated, and the obtained saturation output power is larger than 10 dBm.

A Single-Frequency Linearly Polarized Fiber Laser Using a Newly Developed Heavily Tm3+-Doped Germanate Glass Fiber at 1.95 μm

A compact linearly polarized, low-noise, narrow-linewidth, single-frequency fiber laser at 1950 nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm3+-doped germanate glass fiber. Over 100-mW stable continuous-wave single transverse and longitudinal mode lasing at 1950 nm are achieved. The measured relative intensity noise is less than −135 dB/Hz at frequencies over 5 MHz. The signal-to-noise ratio of the laser is larger than 72 dB, and the laser linewidth is less than 6 kHz, while the obtained linear polarization extinction ratio is higher than 22 dB.

A Compact Low Noise Single Frequency Linearly Polarized DBR Fiber Laser at 1550 nm

A compact low noise single frequency linearly polarized distributed Bragg reflector (DBR) fiber laser based on a 1.4-cm-long homemade Er3+/Yb3+ -codoped phosphate single mode glass fiber has been demonstrated. An over 50 mW stable single frequency linearly polarized fiber laser was achieved. The measured slope efficiency is more than 21.6%, and the signal-to-noise ratio (SNR) is higher than 65 dB and the laser linewidth is less than 2.0kHz. The laser RIN is measured to be less than −150 dB/Hz at the frequencies over 2.0MHz, and the obtained linear polarization extinction ratio (LPER) is more than 30 dB.

Simultaneously Suppressing Low-Frequency and Relaxation Oscillation Intensity Noise in a DBR Single-Frequency Phosphate Fiber Laser

Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward transfer function, which relates the laser output intensity to the pump modulations, is measured and analyzed. A custom two-path feedback system operating at different frequency bands is designed to adjust the pump current directly. The relative intensity noise is decreased by 20 dB from 0.2 to 5kHz and over 10 dB from 5 to 10 kHz. The relaxation oscillation peak is suppressed by 22 dB. In addition, a long term (24 h) laser instability of less than 0.05% is achieved.

Effect of network modifiers on spectroscopic properties of erbium-doped phosphate glasses

The integrated absorption cross section Σabs, peak emission cross section σemi, Judd-Ofeld intensity parameters Ωt (t=2,4,6), and spontaneous emission probability ArR of Er3+ ions were determined for Erbium doped alkali and alkaline earth phosphate glasses. It is found the compositional dependence of σemi is almost similar to that of Σabs, which is determined by the sum of Ωt(3Ω2 + 10Ω4 + 21Ω6). In addition, the compositional dependence of Ωt was studied in these glass systems. As a result, compared with Ω4 and Ω6, the Ω2 has a stronger compositional dependence on the ionic radius and content of modifiers. The covalency of Er-O bonds in phosphate glass is weaker than that in silicate glass, germanate glass, aluminate glass, and tellurate glass, since Ω6 of phosphate glass is relatively large. AR is affected by the covalency of the Er3+ ion sites and corresponds to the Ω6 value.

Spectroscopic properties and thermal stability of Er3+/Yb3+-codoped fluorophosphate glasses

A comprehensive study on the thermal stability and spectroscopic properties of Er3+/Yb3+-codoped Al(PO3)3-based fluorophosphate glasses is reported of the 1.5μm fibre amplifiers in this paper. From optical absorption spectra, the Judd–Ofelt parameters of Er3+ in the glasses and several important optical properties, such as the radiative transition probability, the branching ratio and the spontaneous emission probability, have been calculated by using Judd–Ofelt theory. The fluorophosphate glass exhibits broadband near-infrared emission at 1.53 μm with a full width at half-maximum over 63nm and a large calculated stimulated-emission cross-section of 6.85×10−21cm2.