<DatePicker
  label="Small picker"
  slotProps={{ textField: { size: 'small' } }}
/>
<DatePicker
  label="Picker with helper text"
  slotProps={{ textField: { helperText: 'Please fill this field' } }}
/>
<DatePicker
  label="Filled picker"
  slotProps={{ textField: { variant: 'filled' } }}
/>