A. Sulaiman

Electrically Tunable Microfiber Knot Resonator Based Erbium-Doped Fiber Laser

A compact and tunable fiber laser is demonstrated using a microfiber knot resonator structure made by a highly doped Erbium fiber. A stable laser output is achieved at the 1533-nm region with a signal to noise ratio of 15 dB using a 63-mW 980-nm pump power. With the assistance of a copper wire touching the circumference of the ring, operating wavelength of the proposed laser can be tuned by injecting electric current into the copper wire. The peak wavelength of the laser can be tuned from 1533.3 to 1533.9 nm as the loading current is increased from 0 to 1.0 A. This is due to the thermally induced optical phase shift attributable to the heat produced by the flow of the current. It is also shown experimentally that the wavelength shift is linearly proportional to the square of the amount of current with a tuning slope of 700 pm/A2.

SOA-based multi-wavelength laser using fiber Bragg gratings

We propose and experimentally demonstrate a triple-wavelength fiber ring laser using a semiconductor optical amplifier (SOA) in conjunction with a series of fiber Bragg gratings (FBGs). The three channels operate at 1554.4, 1555.3, and 1556.1 nm with a peak power above −25 dBm and optical signal-to-noise (OSNR) above 30 dB at SOA drive current of 350 mA under the room temperature. The proposed laser configuration has the advantages of a simple and compact structure, multi-wavelength operation and the system can be upgraded to generate more wavelengths by increasing the number of FBG used.

Tunable laser generation with erbium-doped microfiber knot resonator

A tunable laser is demonstrated using a microfiber knot resonator structure made by erbiumdoped fiber (EDF). The laser is made of a 2 m long EDF where 30 mm of its end section is tapered to construct a microfiber knot resonator (MKR). The combination of the EDF and MKR generates a stable single wavelength laser at 1555 nm wavelength with a signal to noise ratio (SNR) of 33.7 dB using a 63 mW of 980 nm pump power. The peak wavelength of the laser can be tuned by 340 pm as the MKR diameter reduces from 5.0 to 0.5 mm with an acceptable penalty in output power.

High-power single-wavelength SOA-based fiber-ring laser with an optical modulator

A semiconductor optical amplifier (SOA) fiber-ring laser (SOAFRL) utilizing a fiber-Bragg grating (FBG) and lithium niobate (LiNbO3) modulator is demonstrated. The laser operates at a wavelength of 1547.64 nm, which is equal to the Bragg wavelength in the saturation region. By removing the LiNbO3 modulator in the ring, the laser shows a single-wavelength output, which has a lower peak power. The experimental results show that when reaching the saturation level, the system with the LiNbO3 modulator shows a higher saturation current and peak power compared to that of the system without the modulator. The effect of varying the modulation frequency on the laser output power is investigated. By incorporating the LiNbO3 modulator in the laser cavity, the side-mode suppression ratio (SMSR) of the laser is significantly improved and a higher peak power can be obtained at a higher current.

Compact and Tunable Erbium-Doped Fiber Laser With Microfiber Mach–Zehnder Interferometer

A compact and tunable Erbium-doped fiber laser is demonstrated using a highly concentrated Erbium-doped fiber in conjunction with a microfiber Mach-Zehnder interferometer (MMZI) structure for the first time. A stable laser output is achieved at 1531.7 nm region with a peak power of -19 dBm and an optical signal to noise ratio of 30.1 dB using a 980-nm pump at 100 mW power. The operating wavelength of the laser can be tuned from 1530.2 to 1532.7 nm by changing the path length difference (PLD) inside the MMZI from 1.6 to 2.7 mm at room temperature. It is also observed that the operating wavelength linearly shifts to a longer wavelength as the PLD increases with a tuning slope efficiency of 0.17 nm/mm. The tuning ability is due to the alteration of the induced optical phase shift inside the MMZI which affects the optical interference and the dominant peak which is responsible for the lasing action.

Compact Dual-Wavelength Laser Generation Using Highly Concentrated Erbium-Doped Fiber Loop Attached to Microfiber Coupler

A compact and low noise dual-wavelength fiber laser is demonstrated using a 70-cm-long Erbium-doped fiber loop attached to a microfiber coupler. The coupler functions to inject a 980-nm pump light as well as to tap out the output. At the maximum pump power of 8.4 mW, dual-wavelength laser is obtained at 1537.7 and 1551.4 nm with peak powers of 20.5 and 20.9 dBm, respectively. Both laser outputs are stable with a signal to noise ratio of more than 35 dB at room temperature. Both 1537.7 and 1551.4 nm lasers start to lase at threshold pump power as small as 2.5 mW with efficiencies of 0.14% and 0.10%, respectively.

Microfiber structures and its sensor and laser applications

Fabrication of various microfiber structures such as loop, knot, mach-zenhder interferometer and coil resonators have been successfully demonstrated using a flame brushing technique. A compact inline microfiber Mach-Zehnder interferometer (MMZI) is also demonstrated for high temperature sensing. The temperature sensitivity of the device was measured to be 13.4 pm/°C with an excellent linearity for temperature measurement up to 800°C. Another MMZI structure is also proposed for application in tunable Erbium-doped fiber laser (EDFL). The operating wavelength of the laser can be tuned from 1530.2 nm to 1532.7 nm by changing the path length difference inside the MMZI from 1.6 mm to 2.7 mm at room temperature.

Erbium-Doped Fiber Laser With a Microfiber Coupled to Silica Microsphere

A compact erbium-doped fiber laser (EDFL) is demonstrated using a piece of 1.5-m-long erbium-doped fiber (EDF) with a microfiber coupled to a silica microsphere at the output end. A stable laser output is achieved due to the recirculation of amplified spontaneous emission (ASE) light inside the linear cavity and the incorporation of microsphere which serves as both a laser filtering element and a mirror. The laser operates at 1533.5 nm with a peak power of 7.7 dBm and an optical signal-to-noise ratio (OSNR) of around 24.4 dB with 980 nm pumping of 100 mW and a sphere diameter of 137 μm. The operating wavelength can be tuned down from 1533.4 to 1531.24 nm by changing the sphere diameter from 108.3 to 190.0 μm. The highest Q-factor of 12760 is obtained at the smallest sphere diameter of 108.3 μm.

Erbium-doped fibre ring laser based on microfibre coupler

A compact erbium- doped fibre (EDF) laser is demonstrated which uses a microfibre coupler and a highly concentrated EDF loop. The coupler functions to inject the pump light and tap out the output. The EDF laser operates at 1526.3 nm, with a signal-to-noise ratio of about 26 dB. The maximum output power 20 µW is obtained at the pump power 18.6mW. We have obtained the slope efficiencies of the laser 0.12, 0.06, 0.04 and 0.02% at the EDF lengths fixed at 90, 78, 66 and 51 cm, respectively. The lowest lasing-pump power threshold is achieved at 3.8 mW

Microfiber-based devices: Current sensor and tunable laser

Microfibers and its knot resonator structure are fabricated using a flame-brushing technique for current sensor and tunable Erbium-doped fiber laser (EDFL) applications. A compact current sensor using a microfiber knot resonator (MKR) is demonstrated based on idea of measuring the thermally induced resonant wavelength shift as a result of heat produced due to the flow of electric current over a copper rod. A tunable fiber laser is also demonstrated using a MKR structure made by a highly doped Erbium fiber. A stable laser output is achieved at 1533nm region with a signal to noise ratio (SNR) of 15dB. With the assistance of a copper wire touching the circumference of the ring, the peak wavelength of the laser can be tuned from 1533.3nm to 1533.9nm as the loading current is increased from 0 to 1.0 A