A broadband continuously tunable semiconductor disk laser is reported in this paper. The active region of gain chip is composed of InGaAs multiple quantum wells with resonant periodic gain structure, and its fluorescence peak wavelength is around 965 nm. Using the wideband characteristics of the quantum wells in gain chip, along with the simple linear cavity that is formed by a high reflectivity external mirror, the laser has a low cavity loss and a wide tuning range. The continuously tunable laser wavelength can be obtained by inserting birefringent filters with different thickness into the cavity. When the thickness of the birefringent filter is 2 mm, the wavelength tuning range of the laser is 45 nm, the maximum output power is 122 mW, and the beam quality M² factors in the X- and the Y-directions are 1.00 and 1.02, respectively. The temperature characteristics of the surface-emitting spectra of gain chip and the narrowing effect of birefringent filter on laser linewidth h are also discussed.