  Time-domain thermoreflectance (TDTR) and frequency-domain thermoreflectance
(FDTR) have been widely used for non-contact measurement of anisotropic thermal
conductivity of materials with high spatial resolution. However, the
requirement of high thermoreflectance coefficient restricts the choice of metal
coating and laser wavelength. The accuracy of the measurement is often limited
by the high sensitivity to the radii of the laser beams. We describe an
alternative frequency-domain pump-probe technique based on probe beam
deflection. The beam deflection is primarily caused by thermoelastic
deformation of the sample surface with a magnitude determined by the thermal
expansion coefficient of the bulk material to measure. We derive an analytical
solution to the coupled elasticity and heat diffusion equations for periodic
heating of a multilayer sample with anisotropic elastic constants, thermal
conductivity, and thermal expansion coefficients. In most cases, a simplified
model can reliably describe the frequency dependence of the beam deflection
signal without knowledge of the elastic constants and thermal expansion
coefficients of the material. The magnitude of the probe beam deflection signal
is larger than the maximum magnitude achievable by thermoreflectance detection
of surface temperatures if the thermal expansion coefficient is greater than
5x10^(-6) /K. The sensitivity to laser beam radii is suppressed when a larger
beam offset is used. We find nearly perfect matching of the measured signal and
model prediction, and measure thermal conductivities within 6% of accepted
values for materials spanning the range of polymers to gold, 0.1 - 300 W/(m K).
