Photosensitivity and Photodarkening of UV-induced Phosphate Glass Fiber Bragg Gratings and Application in Short Fiber Lasers
Bibliographic record
Abstract
Phosphate glass fiber is an ideal choice for building compact high gain fiber lasers, as the fiber can host high concentrations of rare earth ions.However, the low photosensitivity of phosphate glass fibers prevents the integration of UV-written intra-core fiber Bragg gratings (FBGs) into the fiber laser cavity.The research presented in this thesis is focused on the investigation of photosensitivity of UV-written Bragg gratings in phosphate glass fibers and their application in direct-written short monolithic fiber lasers.A systematic investigation of photosensitivity of Er/Yb doped and undoped phosphate glass fibers is carried out using irradiation of intense 193 nm ArF excimer laser light through a phase mask.Thermal annealing experiment results demonstrate that a thermal growth of grating reflectivity of an FBG in phosphate fiber can be obtained upon heating it at temperatures between 100 -250 °C.A recipe that can reliably obtain strong FBGs with final index modulation amplitudes between 5 and 10×10 -5 in phosphate fibers through the photo-thermal process is proposed.An undesirable side effect of FBGs fabrication in a phosphate fiber is discovered that a photodarkening loss of about 1 dB/cm at C-band is also induced by UV irradiation.The photodarkening loss has been identified as the result of formation of a color center at visible band.Photo-bleaching and thermal-bleaching processes are found to be effective in fully erasing the UV-induced photodarkening loss under condition of not diminishing the grating strength.The application of direct-written strong FBGs in building short monolithic phosphate fiber lasers is investigated.A 3.5-cm-long single-wavelength singlelongitudinal-mode distributed feedback (DFB) fiber laser has been implemented in the iii 1%-2% Er/Yb doped phosphate glass fiber.A laser signal with an output power of 27.5 mW at a linewidth of 20 MHz is achieved.In addition, a 5-cm-long monolithic dualwavelength single-longitudinal-mode distributed Bragg reflector (DBR) all-phosphate fiber laser is also demonstrated.By exploiting the polarization hole burning effect and the spatial hole burning effect, stable narrow-linewidth dual-wavelength lasing emission with 38 pm wavelength spacing and a total emitted power of 2.8 mW is obtained from the DBR fiber laser.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".