Optical sampling waveform measuring apparatus aiming at achieving wider band

An optical sampling waveform measuring apparatus comprising:

• a sampling light source which emits a sampling light having a single polarization direction whose pulse width is smaller than that of an inputted measuring object light having a single polarization direction;
• a multiplexer which multiplexes the sampling light emitted from said sampling light source and the measuring object light on the same optical axis such that the polarization directions thereof are perpendicular to each other;
• a nonlinear optical crystal composed of 2-adamantyl-5-nitorpyridine (AANP) allowing type 2 phase matching to the sampling light and the measuring object light, which, when the sampling light and the measuring object light multiplexed by said multiplexer are entered, emits a sum frequency light of said sampling light and said measuring object light, said sum frequency light having a sum angular frequency ωD+ωS based on said measuring object light having an angular frequency ωD and said sampling light having an angular frequency ωS, with the polarization directions thereof being perpendicular to each other;
• incident angle changing means for changing an incident angle of each of the sampling light and measuring object light to be entered into said nonlinear optical crystal into said nonlinear optical crystal;
• a light receiver which converts the sum frequency light outputted from said nonlinear optical crystal to an electric signal;
• a signal processing portion which processes the electric signal outputted from said light receiver so as to display an optical pulse waveform of said measuring object light;
• and
• control means for, when the sum frequency light of said sampling light and said measuring object light is emitted from said nonlinear optical crystal, controlling the polarization direction of said sampling light so as to be parallel to a predetermined reference axis located within a plane perpendicular to a phase matching direction of said nonlinear optical crystal,
• wherein said predetermined reference axis is a single axis maintaining parallelism with a crystalline axis of said nonlinear optical crystal even if the wavelength of inputted light is changed.