Single-photon upconversion via hot-band absorption and assessment of the laser cooling effect of tricarbocyanine dyes

Abstract

A series of new tricarbocyanine near-infrared (NIR) dyes is demonstrated which are able for a single-photon vibronic-assisted anti-Stokes luminescence with a large, up to 147 nm (225 meV), anti-Stokes shift of the excitation energy. It is shown that quantum yield of the anti-Stokes emission depends on both the dye substituents, which bear different charge, and the energy of the excitation light. It is demonstrated that higher excitation energy captures electrons from the deeper vibronic levels and thus yields brighter anti-Stokes emission. It was found that skeletal CNC in-plain bending deformation of the chromophore chain with an activation energy of 55±8 meV is mainly responsible for supplying the hot band with electrons, even if the hot-band absorption occurs from the higher vibronic level corresponding to the CN stretch (~1360 cm−1). It is shown that dye solutions with the brighter anti-Stokes emission possess a better laser cooling effect, which is dependent on population of the hot band and reaches up to 1 K at solution temperature of 80 °C.

Keywords

• Near-infrared dye
• Hot-band absorption
• Anti-Stokes emission
• Laser cooling