FORTH-Experiment DALHM meeting 18 / 09 / 2003 Heraklion, Crete

Milestones and expected results (T0+12) M1.1 Modeling of LH structures M1.2 Physical characterization of 1D LH structures M2.1 Fabrication of 1D LH structures M3.1 Modeling and characterization of LH antenna

1D LH test structures LH structures tested: ax = 5 mm, ay= 3.63 mm, PCB boards (5-15 GHz, design of Bilkent) fabrication: printed circuit board technology ax = ay= 0.5 mm, GaAs substrates (25-40 GHz) fabrication: UV lithography technique

SRR parameters for 5-15 GHz for 25-40 GHz ax = 5 mm, ay= 3.63 mm w = 3 mm c = 0.33 mm g = 0.33 mm d = 0.33 mm for 25-40 GHz ax = ay= 0.5 mm w = 0.26 mm c = 0.02 mm g = 0.04 mm d = 0.03 mm

GaAs-based CMMs (measurements at Bilkent)

Theoretical calculations for GaAs-based CMMs at FORTH

GaAs-based CMMs (measurements at FORTH) ωp2 = 2πc02 / α2 ln (α / r)

We have to be extremely careful with the assignment of LH behavior to CMMs. The SRR “dip” coincidence with a CMM “peak” is not necessarily a proof for LH behavior. The “wires” – only structures are necessary to get an idea for the “plasma freq.” of the CMM. However, this is at the same time misleading since we have also to take into account the interactions between the wires and the SRRs which definitely alter the electric response of the CMM.

We are currently working on producing SRRs- and wires- only structures on GaAs. However, since we now expect this GaAs-based CMM not to show a LH peak (after present theoretical calc.), we are thinking of adding a second wire in the unit cell so that we might shift the “plasma freq.” (ωp´) higher.

CMM on PCB boards

Dependence of the SRR response on αz-separation

Dependence of the in-plane CMM response on αz-separation

Dependence of the off-plane CMM response on αz-separation

Observations Broadening of the CMM peak with increasing αz separation in both the in-plane and off-plane CMMs. The SRR response is not strongly affected. The broadening of the CMM peak is due to the shift of the wires-only “plasma freq.” to lower freqs. Are the observed peaks really LH?

Characteristic frequencies of the CMM αz= 5.5mm

Cut-SRR Closed-SRR

Switching on and off the magnetic response of the SRR

Conclusions We must extensively check one structure before concluding that it shows LH behavior. The critical frequency for the electrical response of the CMM is ωp΄. We must though be able to control ωp΄ in relation with ωm. In order to safely design real LH structures we have either to shift ωp΄ higher or ωm lower.

Ongoing work - Future plans Understand the different parameters that affect ωp΄ and ωm (wires width, resonator gap, distance between rings etc.). Target tailor-made 1D LH structures. Continue the work on the 30GHz GaAs-based structures (trying to produce real LH peaks). Investigate the simple SRR behavior (is there really there a LH peak?). Start working with 2D structures as well as with THz structures.