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Poled fiber devices
KTH, School of Engineering Sciences (SCI), Physics.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The topic of this thesis is the development of devices for telecom applications based on poled optical fibers. The focus is on a specific function, optical switching/modulation.

Some of the most important results are summarized below. Optical switching at telecom wavelengths (1.55 μm) is demonstrated in an all-fiber switch based on a fiber with internal electrodes. The fiber is made electro-optically active with a thermal poling process in which a strong electric field is recorded in the glass at a temperature of 255 °C. After poling, the fiber is put in one arm of a Mach-Zehnder interferometer and by applying a voltage across the two electrodes the refractive index is modulated and the optical signal switched from one output port to the other. A switching voltage of 190 V at 1550 nm was achieved, which to the best of our knowledge is the lowest value reported. By carefully matching the lengths of the fibers in the two arms of the interferometer the optical bandwidth could be made as large as 20 nm. The extinction ratio, determined by the power ratio in the two arms, was 30 dB and the highest modulation frequency was 30 MHz. Poled fibers were packaged to increase the thermal and mechanical stability and to make handling easier. 40 Gb/s transmission test through the device showed no bit-error-rate performance degradation. Protection switching of a 10 Gb/s signal is also demonstrated.

The depletion region in a poled fiber was found to be wedge-shaped and very wide, 13 μm and completely overlapped with the core. In a time-resolved poling experiment the recorded electric field was measured. The sign of the field changed after ~20 min, when the depletion region passed through the core, which led to the conclusion that an electric field is present also outside of the depletion region.

A ring laser was constructed with an erbium doped fiber as the gain medium. A fiber modulator was placed inside the cavity and when a small RF signal, with a frequency matched to the cavity ground frequency, was applied to the modulator the laser was modelocked. The output pulse train contained pulses of sub ns duration and is the first demonstration of mode-locking using poled fibers.

A sampled grating with 16 channels spaced by 50 GHz was inserted into the cavity. The fiber modulator had optical bandwidth of 7 nm with center wavelength that depends on the applied voltage. By applying of 10 – 210 V to the modulator it was possible to tune the laser to 11 of the 16 channels for a total tuning range of over 4 nm.

A scheme to deposit 1 μm thin silver electrodes inside the holes of an optical fiber is demonstrated together with a new method of creating periodic electrodes by periodically ablating the silver film electrodes. The periodic electrodes are used to create a quasi-phase matched (QPM) nonlinearity in a fibers which is showed in a proof of principle experiment.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 77 p.
Series
Trita-FYS, ISSN 0280-316X ; 2005:22
Keyword [en]
Physics, optical physics, Poling, twin-hole fiber, fiber electrodes, silver film electrodes, silver diffusion, quasi-phase matching, optical switching, frequency conversion, optical modulation
Keyword [sv]
Fysik
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-262ISBN: 91-7178-053-X (print)OAI: oai:DiVA.org:kth-262DiVA: diva2:8273
Public defence
2005-06-10, Sal FD5, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101015Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2015-03-30Bibliographically approved
List of papers
1. A Fibre-Based Kerr Switch and Modulator
Open this publication in new window or tab >>A Fibre-Based Kerr Switch and Modulator
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2004 (English)In: 30th Eruopean Conference on Optical Communications: Stockholm, Sweden. Sept 2004, 2004Conference paper, Published paper (Refereed)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5271 (URN)
Note
QC 20101015Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2010-10-15Bibliographically approved
2. Measurement of Depletion Region Width in Poled Silica
Open this publication in new window or tab >>Measurement of Depletion Region Width in Poled Silica
2005 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, no 27, 5793- p.Article in journal (Refereed) Published
Abstract [en]

The width of the depletion region in fused-silica samples thermally poled during various periods of time is investigated experimentally with four previously reported characterization techniques in an attempt to unify their findings. Although all measurements give a similar width of the depletion region, it is shown that the determination of the profile of chi((2)) is also required for a good estimate of the nonlinearity induced by poling.

Keyword
fused-silica, 2nd-order nonlinearity, charge-distribution, glass, dynamics, profile
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5272 (URN)10.1364/AO.44.005793 (DOI)000232119100023 ()2-s2.0-27144460691 (Scopus ID)
Note
QC 20101015Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
3. In-fiber electrode lithography
Open this publication in new window or tab >>In-fiber electrode lithography
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2004 (English)In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 21, no 12, 2085-2088 p.Article in journal (Refereed) Published
Abstract [en]

The fabrication of meter-long continuous internal fiber electrodes is achieved through deposition of a silver film inside a twin-hole fiber. Photolithography of the electrodes with 5-μm resolution inside the fiber is demonstrated by point-by-point side exposure to 0.53-μm radiation through the unharmed acrylate coating, causing laser ablation. A proof-of-principle experiment demonstrates the creation of a phase-matched structure for frequency doubling.

Keyword
Chemical vapor deposition, Electrodes, Laser ablation; Light absorption, Metallic films, Natural frequencies, Optical fibers, Optical microscopy, Photolithography, Scanning electron microscopy
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5273 (URN)10.1364/JOSAB.21.002085 (DOI)000225666900002 ()2-s2.0-11244277076 (Scopus ID)
Note
QC 20100920Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
4. Wide wedge-shaped depletion region in thermally poled fiber with alloy electrodes
Open this publication in new window or tab >>Wide wedge-shaped depletion region in thermally poled fiber with alloy electrodes
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2004 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 12, no 25, 6093-6099 p.Article in journal (Refereed) Published
Abstract [en]

A twin-hole fiber was provided with Au-Sn alloy electrodes and thermally poled at 255 degreesC with 4.3 kV applied during 155 minutes. An electric field 6 x 10(7) V/m was recorded. The poled fiber was cleaved and etched, revealing that the depletion region overlapped the entire core, was wedge shaped and pointed towards the cathode. The recorded profile closely followed the spatial distribution of the poling field.

Keyword
2nd-order nonlinearity, silica, field
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5274 (URN)10.1364/OPEX.12.006093 (DOI)000225708300002 ()
Note
QC 20101015Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
5. Time evolution of frozen-in field during poling of fiber with alloy electrodes
Open this publication in new window or tab >>Time evolution of frozen-in field during poling of fiber with alloy electrodes
2005 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 13, 3438-3444 p.Article in journal (Refereed) Published
Abstract [en]

Twin-hole fibers were provided with Au-Sn alloy electrodes and thermally poled at 255 ° C. The evolution of the depletion layer was studied by etching fibers poled at varying poling temperatures. The electro-optic response was measured for different poling times. When the depletion region did not overlap the core the direction of the recorded field was opposite to the applied poling field. Poling for a longer time made the depletion region extend through the core and changed the sign of the recorded field.

Keyword
poled fused-silica, 2nd-order nonlinearity, dynamics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5275 (URN)10.1364/OPEX.13.003438 (DOI)000228896200028 ()2-s2.0-21244483893 (Scopus ID)
Note
QC 20101015Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
6. All-fiber electrooptical mode-locking and tuning
Open this publication in new window or tab >>All-fiber electrooptical mode-locking and tuning
2005 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 17, no 10, 2047-2049 p.Article in journal (Refereed) Published
Abstract [en]

Active mode-locking of a fiber laser with an all-fiber electrooptic modulator is demonstrated. A 1.4-V driving signal was used, creating subnanosecond single pulses at the fundamental frequency of the cavity (12 MHz). The modulator was a packaged Mach-Zehnder interferometer incorporating a poled twin-hole fiber in one of the arms. The switching voltage was 230 V at 1550 nm, with extinction ratio similar to 20 dB. The interferometer could be electrooptically tuned by 3.5 nm.

Keyword
fiber ring lasers, laser tuning, mode-locked lasers, pulsed laser
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5276 (URN)10.1109/LPT.2005.856390 (DOI)000232149600014 ()2-s2.0-26844573018 (Scopus ID)
Note
Uppdaterad från submitted till published: 20101015. QC 20101015Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
7. Systems measurements of 2x2 poled fiber switch
Open this publication in new window or tab >>Systems measurements of 2x2 poled fiber switch
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2005 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 17, no 12, 2571-2573 p.Article in journal (Refereed) Published
Abstract [en]

The performance of a 2x2 all-fiber electrooptical switch is characterized in a system at up to 40 Gb/s. Error-free transmission is demonstrated. The device was also employed as a protection switch at 10 Gb/s in an installed fiber link.

Keyword
electrooptic modulation, integrated optoelectronics, optical fiber communication
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-5277 (URN)10.1109/LPT.2005.859126 (DOI)000233621000024 ()
Note
QC 20101015Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved

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