Temperature sensing probes for sensing the temperature of a substrate based on fluorescence are disclosed. The temperature sensing probes include a fiber optic cable having at a cold end an optical interface and at a hot end a temperature sensing element for contacting a substrate. A sheath surrounds at least a portion of the hot end of the fiber optic cable. A retaining member securely and removably engages the sheath with a support member. The sheath forms a vacuum seal around the contact between the temperature sensing element and the substrate.