Highly efficient and compact acousto-optic modulator of a fibre Bragg grating is reported for the first time. The device is composed of millimetre scaled components and a 1 cm grating inscribed in a four air holes birefringent suspended core fibre. The reflection of the orthogonal polarization modes is tuned by a sinusoidal electrical signal at the resonance frequency of 469 kHz. A significant modulation depth of 45% is achieved at a maximum drive voltage of 10 V. The demonstrated 4 cm long all-fibre modulator is 60% shorter compared to previous similar setups, indicating new possibilities for stable and fast switching of fibre-integrated photonic devices.
The confinement of high frequency acoustic waves inside a suspended core fibre (SCF) is numerically investigated for the first time. A 500 μm long acoustic cavity, based on a four-hole SCF, is designed, simulated and evaluated by using the finite element method. The cavity is acoustically excited in the frequency range of 50 - 56 MHz and the induced displacements are integrated along the fibre. A standard single mode fibre is simulated under the same conditions for comparison. The results show strong Lamb acoustic modes oscillating in the silica bridges and overlapping in the SCF core at the resonance of 52.84 MHz. The induced displacement achieves a maximum in the core centre decaying to an almost null value in the cladding. The acoustic wave concentration in the SCF core is 13 times higher compared to the standard fibre, indicating a promising solution to overcome the frequency limitation of the current all-fibre acousto-optic devices. The modulation efficiency is increased without reducing the fibre diameter, making the devices more stable, fast and suitable to modulate all-fibre lasers.
The interaction of a fiber Bragg grating and longitudinal acoustic waves in a highly birefringent suspended-core fiber is investigated for the realization of a multi-wavelength reflection property. The modulated grating couples power from the fast and slow polarization modes to shifted superposed modes supported by the grating. The grating reflectivity of the superposed modes are tuned by the voltage of an electrical signal. Up to five different wavelength reflection peaks have been generated indicating new possibilities for compact and fast fiber-integrated multi-wavelength dynamic filters.
An ytterbium-doped fiber laser mode-locked by the interaction of a fiber Bragg grating and longitudinal acoustic waves in a suspended core fiber is experimentally investigated. An optimized design of an acousto-optic modulator is also proposed. The results indicate output pulses with a width of less than 550 ps at a repetition rate of 10 MHz. The reduction of the power consumed by the transducer and the grating length points out to more efficient, compact and fast acousto-optic modulators for mode-locked all-fiber lasers.
Longitudinal acoustical modes propagating in a fiber are characterized using an extrinsic Fabry-Perot interferometer. The
method allows the detection of the fiber axial deflection peaks which correspond to the acoustic resonances. The method
can be further used for estimating properties of acoustic excited fibers, such as acoustic frequency and wavelength,
which are essential in the design of acousto-optic devices employing Bragg gratings.
The development of a fiber extrinsic Fabry-Perot interferometer for measuring vibration amplitude and resonances of
piezoelectric elements is reported. The signal demodulation method based on the use of an optical spectrum analyzer
allows the measurement of displacements and resonances with high resolution. The technique consists basically in
monitoring changes in the intensity or the wavelength of a single interferometric fringe at a point of high sensitivity in
the sensor response curve. For sensor calibration, three signal processing techniques were employed. Vibration
amplitude measurement with 0.84 nm/V sensitivity and the characterization of the piezo resonance is demonstrated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.