Micromirrors and diffraction gratings were developed for spectroscopy and magnetic field sensor in this thesis. MEMS blazed gratings were successfully fabricated in different grating periodicities to cover a wide infrared wavelength range. Lorentz force actuated micromirrors were investigated, and two types of mirrors were fabricated: rotating and pop-up micromirrors. The deflection angle of the mirrors was controllable by altering the driving current on the mirror. Deflection angle vs. driving current was studied for different mirror types and different spring dimensions. A Lorentz force based magnetic field sensor is also demonstrated. The sensor employs the rotating micromirror as a resonator. With an AC current flowing around the micromirror, a periodic Lorentz force is generated which drives the resonator. The rotational amplitude of the micromirror is measured with an optical positioning system and external circuits. The highest resolution of the magnetic field sensor is 0.4 nT at 50 mArms, and 53 mHz filter bandwidth. With appropriate current level, this sensor can measure a wide range of magnetic field, from nT to T. / October 2016