High Q factor bonding using natural resin for reduced thermal noise of test masses

Abstract

We show that a low acoustic loss resin enables composite mechanical structures to be bonded with minimal Q degradation. The resin is excreted from the Australian native grass tree Xanthorrhoea. This resin has traditionally been used as an adhesive by the Australian Aborigines. It is shown that the Q factor of the resin is greater than 300 for the 5180 Hz resonance, which allows a high Q factor niobium resonator to be constructed with bonded mirrors while maintaining a Q of ϳ10 6 .Internal test mass thermal noise is a limiting noise source in the middle frequency range ͑ϳ30-500 Hz͒ for interferometric gravitational wave detectors, 1 and also in many other precision mechanical experiments. Investigations into bulk thermal noise have been conducted by several gravitational wave groups. [2][3][4][5][6] In sensitive experiments it is often necessary to attach objects such as mirrors or magnets to the primary test mass. 7,8 However, this invariably introduces additional thermal noise through the acoustic loss of the bonding agent. For many years gravitational wave researchers have been studying low loss bonding to minimize this effect. The most successful is silicate bonding. 9,10 Silicate bonding, however, involves a molecular bond which only works effectively between certain materials. Silicate bonds also require a long time to set and are irreversible.In this note we show that a bonding agent, traditionally used by the Australian Aborigines, has a low acoustic loss compared with more conventional adhesives. We show experimentally that bonding agents with varying intrinsic acoustic losses can significantly affect the Q degradation of composite structures. We have also used a one-dimensional lumped parameter model to study bonded composite structures, which has been compared to experiment.

High quality factor mg-scale silicon mechanical resonators for 3-mode optoacoustic parametric amplifiers

“…A maximum quality factor value of 9 Â 10 4 was obtained by clamping the wafer at various locations along the edges and corners. Bonding our sample with Yacca gum, a natural resin with low intrinsic loss, 20 also produced quality factors too low for our requirements (6 Â 10 4 ), as we found the isolation provided by the paddles and torsion rods were insufficient for our required level of quality factors.…”

A micromechanical proof-of-principle experiment for measuring the gravitational force of milligram masses

“…We may then integrate the energy density in the deflected state for all individual components of the system for any given mode, allowing us to calculate Q using the above expression. The individual Q-values were gathered as follows: For the adhesive, a Q adhesive value of "more than 300" at room temperature has been reported in [28]. As a substrate we assume AlGaAs, similar to the devices in [29], with a room temperature Q substrate ≈ 30,000.…”

“…It turns out that in a simple cantilever-geometry the mechanical quality of the material directly at the bonding surface between cantilever and test mass can have a huge negative impact on the overall quality of the compound system. This can be circumvented by changing the cantilever geometry such that deformation of the bonding surface is avoided, or by attaching the test mass to the cantilever using an adhesion layer with low internal losses [28]. A specific example is presented in Appendix C. Assuming Qs of 30,000 for an AlGaAs cantilever [29], 300 for the adhesive [28] and 100 for the test mass one obtains the overall dissipation by adding up the loss angles and at the same time scaling their contribution with the mode stress derived from FEM simulations, which yields quality factors of the mass-loaded structure of at least Q ≈ 24,000.…”

“…This can be circumvented by changing the cantilever geometry such that deformation of the bonding surface is avoided, or by attaching the test mass to the cantilever using an adhesion layer with low internal losses [28]. A specific example is presented in Appendix C. Assuming Qs of 30,000 for an AlGaAs cantilever [29], 300 for the adhesive [28] and 100 for the test mass one obtains the overall dissipation by adding up the loss angles and at the same time scaling their contribution with the mode stress derived from FEM simulations, which yields quality factors of the mass-loaded structure of at least Q ≈ 24,000. A brief estimation of damping through Brownian noise from gas impacts is presented in Appendix D.…”

Classical demonstration of frequency-dependent noise ellipse rotation using optomechanically induced transparency

“…In order to adjust the position and alignment of the membrane in the vacuum, it was attached to a piezoelectric actuator which was glued to a motorized optical mounts attached to the invar cavity spacer. To reduce the bonding loss, the membrane frame was bonded onto the actuator with Yacca gum, a natural resin with low intrinsic loss [26]. After gluing, we measured the quality factor of the membrane with a He-Ne laser to characterize the extra mechanical loss γ gas introduced by the background gas.…”