Writing low-loss waveguides in borosilicate (BK7) glass with a low-repetition-rate femtosecond laser

• Published in: Optics communications 2011-01, Vol.284 (2), p.630-634
• Main Authors: Dharmadhikari, J.A., Dharmadhikari, A.K., Bhatnagar, A., Mallik, A., Singh, P. Chandrakanta, Dhaman, Reji K., Chalapathi, K., Mathur, D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Borosilicate; Borosilicate glass; Borosilicate glasses; Energy dose window; Exact sciences and technology; Femtosecond; Femtosecond laser writing; Fundamental areas of phenomenology (including applications); Glass; Lasers; Material modification; Nonlinear optics; Optical elements, devices, and systems; Optical telecommunications; Optical waveguides and coupleurs; Optics; Physics; Slits; Telecommunications; Telecommunications and information theory; Ultrafast laser; Ultrafast processes; optical pulse generation and pulse compression; Wave optics; Wave propagation; Wave propagation, transmission and absorption; Waveguide writing; Waveguides
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2010.09.055

Borosilicate glass (BK7) is a widely-used material in integrated optics devices and in the optical communications industry. We report on laser-written waveguiding in BK7 glass using a low-repetition-rate (1 kHz) laser producing 40 fs pulses of 800 nm light. A 500 μm slit is used to write structures 100 μm below the glass surface. These waveguides show strong guidance at 635 nm, with an index contrast of 3 × 10 − 4 and a propagation loss of ~ 0.5 dB/cm. We measured the change in refractive index for a range of writing conditions as quantified in terms of energy dose; there is an energy dose window (> 0.6 μJ μm − 3 and < 1.5 μJ μm − 3 ) within which the written structures show guidance.