As we have seen in the previous Chapters, a single strongly-focused laser beam is a powerful tool to trap and manipulate microscopic particles. Furthermore, we have seen in Chapter 11 that multiple and dynamic optical tweezers can be generated using diffractive optics. However, this does not exhaust the potential of optical trapping and manipulation. Indeed, as optical forces have been applied to the so- lution of problems in different fields, they have been adapted to and hybridised with the techniques available and needed in these fields. An example of such an advanced hybrid application is shown in Fig. 12.1, where a feedback optical trap is used to hold a nanoparticle in a bow-tie nanoaperture fabricated on the tip of a ta- pered metallised optical fibre. In this Chapter, we will survey these more advanced techniques, i.e., the hybridisation of optical tweezers and spectroscopic techniques, the generation of extended optical force landscapes, the use of optical fibre traps, evanescent wave traps and feedback traps, and the exploitation of haptic devices to interface the microworld and the user.
12.1 Spectroscopic optical tweezers
12.1.1 Fluorescence tweezers
12.1.2 Photoluminescence tweezers
12.1.3 Raman tweezers
12.2 Optical potentials
12.2.1 Periodic and quasi-periodic potentials
12.2.2 Random potentials and speckle tweezers
12.3 Counter-propagating traps and optical fibre traps
12.3.1 Optical stretcher
12.3.2 Longitudinal optical binding

12.4 Evanescent wave traps
12.4.1 Evanescent tweezers
12.4.2 Waveguides
12.4.3 Optical binding
12.4.4 Plasmonic traps
12.5 Feedback traps
12.6 Haptic optical tweezers
References
Figure 12.1 — Self-induced back action optical trap
Figure 12.2 — Basic configurations of spectroscopic optical tweezers
Figure 12.3 — Concrete implementations of spectroscopic optical tweezers
Figure 12.4 — Experimental realisation of colloidal quasicrystals
Figure 12.5 — Speckle optical tweezers
Figure 12.6 — Counter-propagating optical traps
Figure 12.7 — Optical fibre traps
Figure 12.8 — Evanescent wave trapping
Figure 12.9 — Optical waveguide forces
Figure 12.10 — Evanescent optical binding
Figure 12.11 — Plasmonic traps
Figure 12.12 — Self-induced back action traps
Figure 12.13 — User interfaces for controlling haptic optical tweezers