On-chip Raman Laser On A Silica Microdisk Resonator

Silica microcavity has received extensive attention in various research fields because of their high optical quality factor Q and small mode volume.For example,cavity opto-mechanics,cavity quantum electrodynamics,micro lasers,biosensors,filters,nonlinear optics,etc.And because it can be easily integrated with other on-chip optical devices,it has great application prospects in optical communications and computers.In this paper,we first described the fabrication of various sizes of large wedge-angle silica microdisk by the process of induced coupled plasma dry etching.First,we demonstrsted optical microcavities whose diameters are 80?m and thicknesses are 1?m,2pm,3?m,respectively,while the corresponding optical quality factors of 1.2 × 107,2.1 × 107,3.0 × 107.Because of their small size,these optical microdisks have a small mode volume,and can obtain a large light energy density in the cavity,So Raman lasers can be generated at lower threshold conditions.Moreover,the wedge angle of the dry-etched microdisk cavity can be made very large,which is very suitable for integration with other optical devices.Besides,we fabricated large-diameter microdisks whose diameters are 80?m,500?m,1000?m,2000?m,and 3000?m,respectively with the thicknesses of 4?m.And the quality factor of such large-diameter microdisks all can be reach 107.These large-diameter microdisks,because of their relatively small free spectral range(FSR),have an important application in optical frequency combs.Moreover,the wedge angle of these large-diameter microdisk cavities can also be adjusted within a large range,which can effectively control the dispersion of light in the cavity,and can generate optical frequency combs in various wavelength bands.Then we introduced an on-chip Raman laser on a silica microdisk.So far,silica Raman microlasers have been demonstrated in sphere,toroid,and bottle-like resonators,in which a CO2 laser is employed to assist the fabrication of the devices.In this work,we experimentally demonstrated a different silica Raman microlaser using an on-chip microdisk resonator coupled to a tapered optical fiber.The major advantage stems from the fact that the fabrication of this microlaser does not rely on the reflow process and thereby elegantly avoids the deleterious impacts on the microcavities' shape.So it is more convenient to intergrate with other optical devices.In the experiment,Raman laser was obtained by using a silica microdisk with an intriasic optical Q-factor of 1.5×107 at 1550nm band,the threshold of the Raman lasering is 3.9 mw with a conversion efficiency of 7.5%.At last,we demonstrated an optical frequency comb based on a large-diameter,large wedge-angle silica microdisk.In the experiment,we measured the threshold of optical frequency comb is about 630?w with a 4?m-thickness,500pm-diameter optical microdisk resonator.